CLINAL VARIATION IN THE APPENDICULAR SKELETON OF JUVENILES
Jennifer Laurel Lloyd
B.B. A., University of Houston, 1999
A thesis submitted to the
University of Colorado at Denver
in partial fulfillment
of the requirements for the degree of
Master of Arts
This thesis for the Master of Arts degree
Jennifer Laurel Lloyd
has been approved by
Lloyd, Jennifer L. (M.A., Anthropology)
Clinal Variation in the Appendicular Skeleton of Juveniles
Thesis directed by Associate Professors Gail Krovitz and David Tracer
Environmental factors such as temperature and climate have been used to
explain some of the morphological variation found in geographically disparate
populations of warm-blooded animals including humans. In particular, Allens rule
addresses how temperature will affect the shape of a group following thermodynamic
principles, while Bergmanns Rule addresses overall size. Populations living in
colder climates will tend to exhibit higher body mass values (increasing heat
production) and shortened limb segments (reducing relative surface area and
therefore, minimizing heat loss). Conversely, in tropical environments, more linear
body forms are to be expected. While this has been well documented in adult
populations, there is little research documenting when these body proportions appear
There are several ways of assessing differences in body form, but one method
is to examine limb proportions. Brachial and crural indices were analyzed for
archaeological populations containing both adults and juveniles from Sudanese
Nubia, Alaska and the Aleutian Islands, and Thailand. Low index values would be an
indication of adaptation to cold and high values would indicate adaptation to warm
climates. Analysis of variance and t-tests for independent samples were used to
determine if statistically significant differences between populations existed. The
same methods were used to determine if assigned age ranges exhibited any variation
within and between populations.
Results from this study indicate that while the adult reference samples are
characterized by index values consistent with clinal variation, results for juveniles are
less straightforward. Juveniles did exhibit patterns of clinal variation in later
childhood with the Alaskan/Aleut sample demonstrating cold-climate index values
and the Nubian and Thai populations exhibiting warm-climate values. However, fetal
and infant groups were markedly different with all three populations exhibiting high
values, suggesting that clinal variation may not be apparent until later in
development. Therefore, results from this study suggest that further research to
examine the factors responsible for the variation in indices found in this study is
This abstract accurately represents the content of the candidates thesis. I recommend
For my father, C. Jerre Lloyd, who gave me immense amounts of mental, emotional
and financial support throughout this process.
My thanks to David Hunt at the National Museum of Natural History and Dennis Van
Gerven at the University of Colorado at Boulder for allowing me access to the
Alaskan and Nubian collections at their respective institutions. Additionally, I would
like to thank the Department of Anthropology at the University of Colorado at
Denver and Health Sciences Center for providing me with funding to travel to the
Smithsonian. Within the Department of Anthropology, I would like to acknowledge
all who gave me guidance and support, particularly Connie Turner for her mothering.
I am greatly indebted to Gail Krovitz for starting me in the right direction on this
project and for helping me continuously along the way. Also, my other committee
members, David Tracer and Charles Musiba, for valuable feedback and patience.
Lastly, I wish to thank Megan Wilson, Amy Lloyd and Nate Kresse for constantly
reminding me that I could do it.
Evidence of Ecogeographical Patterning...................6
Alternative Explanations for Selection in Body Form.....10
Climatic Adaptation in Children.............................13
3. RESEARCH DESIGN...............................................20
Brachial and Crural Indices.................................21
Specific Questions and Predictions..........................21
4. MATERIALS AND METHODS.........................................24
Khok Phanom Di..........................................29
Additional Populations with Published Data
Within Population Variation.................................44
Comparison to Published Data and Research...................74
LIST OF FIGURES
5.1 Mean Values for Adult Long Bones........................................39
5.2 Mean Values for Adult Indices...........................................40
5.3 Mean Values for Juvenile Indices........................................53
5.4 Brachial Indices By Age Group For Study Populations.....................59
5.5 Crural Indices By Age Group For Study Populations.......................59
5.6 Brachial Indices By Age Group For Study Populations
And Additional Published Populations....................................63
5.7 Crural Indices By Age Group For Study Populations
And Additional Published Populations....................................64
5.8 Plot of Mean Index Values Versus Latitude...............................64
6.1 Mean Humeral Values for Study Populations by Age Group..................69
6.2 Mean Radial Values for Study Populations by Age Group...................69
6.3 Mean Femoral Values for Study Populations by Age Group..................70
6.4 Mean Tibial Values for Study Populations by Age Group...................70
6.5 Brachial Indices by Age Group with Trendlines...........................72
6.6 Crural Indices by Age Group with Trendlines.............................72
LIST OF TABLES
4.1 Number of measurements available for sample populations..............30
4.2 Number of measurements available for juveniles
by population and age category......................................36
5.1 Descriptive statistics for adults....................................41
5.2 Comparison of adult mean indices, ANOVA results......................42
5.3 Comparison of adult mean values by limb bone,
5.4 Comparison of adult indices by sub-population,
5.5 Descriptive statistics of adult subpopulations.......................47
5.6 Mean measurements by sex and population..............................49
5.7 Comparison of mean differences by sex, T-test results................50
5.8 Comparison of brachial indices by sex, ANOVA results.................51
5.9 Comparison of crural indices by sex, ANOVA results...................51
5.10 Comparison of juvenile mean indices, ANOVA results...................53
5.11 Mean values of measurements for juveniles
by population and age group.......................................55
5.12 Comparison of juvenile mean indices by age group,
The study of human variation is a key focus in the discipline of anthropology.
The morphological variability exhibited by our species has been quantified in many
ways and attributed to various causes including nutrition, family size, socio-
economic status, competition, and climate (Boas, 1912; Coon et al., 1950; Hulse,
1960; Kennedy, 1976; Eveleth and Tanner 1990; Bogin, 1995). It is with this last
element, climate, that the present study is concerned, though all of the
aforementioned variables may act on a population to influence the process of natural
Since the mid-nineteenth century, environmental factors such as temperature
and climate have been used to explain the variation of body form found in
geographically disparate populations. Ecogeographical patterns of body size and
shape are well established in humans and other homeothermic animals (Allen, 1877;
Mayr, 1956; James, 1970; Roberts, 1953; Roberts, 1978; Ruff, 1994; Katzmarzyk
and Leonard, 1998). More specifically, Allens rule addresses how temperature
affects the shape of an organism, particularly its extremities, while Bergmanns rule
addresses overall body size (Bergmann, 1847, translated in James, 1970; Allen,
1877). Populations living in colder climates will tend toward higher body mass,
thereby increasing heat production. At the same time these groups will possess
shortened limb segments, which reduces relative surface area and thereby minimizes
heat loss. Conversely, organisms found in tropical climes are expected to exhibit
more linear body forms with proportionally longer and more slender extremities,
which maximize relative surface area of the body and therefore heat loss. While
climatic variables may also be linked to variation in physiological mechanisms
within the body, I am primarily concerned with metric variation in body form for the
Although this clinal variation in body form has been well documented (Ruff,
1994), the mechanisms responsible for this climatic patterning are less clear. Many
researchers consider the range of variation found in body shape and size across
climatic zones to be the result of long-term genetic adaptation (Benoist, 1975; Ruff,
1994; Holliday, 1997a; Pretty et al., 1998; Holliday 1999). However, several studies
conclude that differences are due to organisms plastic response to immediate
stresses, whether climatic or as the result of other environmental factors such as
nutrition (Scholander, 1955; Hulse, 1960; Weaver and Ingram, 1969; Riesenfeld,
1981; Martorell et al., 1988). One way of rectifying this debate is by determining
whether or not climate-related body form variation among populations is readily
apparent in juveniles and at what point in development any variation appears.
Presumably, genetically controlled characteristics may be present early in life, while
those that are largely the result of developmental processes will not become apparent
until later, during postnatal growth. Of course this is an oversimplification of
potential patterns and it is equally possible that both genetic and developmental
factors play a role in ecogeographical patterning of body form.
A variety of stressors, including poor nutrition and disease, can impact peri-
and postnatal development, resulting in decreased body size and potentially
increasing within-group variation and skewing any cross-populational comparisons.
However, previous research (Katzmarzyk and Leonard, 1998) suggests that the
relative lengths of limb segments are less susceptible to change as a result of non-
climatic stress. Therefore, comparing the relative lengths of limb segments is one
way to assess variation in body form (as predicted by Allens rule) with minimal
impact from other potential environmental variables. Two indices are often used in
this type of assessment: the brachial index (radial length/humeral length 100) and
the crural index (tibial length/femoral length 100).
Skeletal remains from archaeological populations are ideal for this type of
metric data analyses and are likely, due to antiquity, to represent more genetically
homogeneous groups than many present day populations. The primary skeletal
collections included here are from Sudanese Nubia, Alaska and the Aleutian Islands,
and Thailand. They are well suited for examining evidence of climatic variation
during growth because they contain fairly large numbers of juvenile specimens with
post-cranial remains. Additionally, these collections represent a broad range of
climate types hot/arid, cold, and hot/humid, respectively. Anthropometric data
from individuals are used for each of these populations, but to increase the
geographic representation of this study, published mean data from additional regions
are included for discussion. The goal of this study is to assess the extent of variation
in brachial and crural indices found among juvenile individuals in these populations.
My specific aims are to:
1. Establish the level of variation in brachial and crural indices present between
adult reference samples and determine if variation is related to climate.
2. Determine to what extent juvenile brachial and crural indices reflect those of
the adults from the same sample and assess any variation among the
juveniles. Specifically, to determine if variation is a function of age or of a
particular limb segment within a single skeletal collection.
3. Discern any patterns in limb proportions during growth within a group and
compare across populations.
While there are many ways to assess variation in humans, the analyses of
those mechanisms that influence skeletal development are of importance because
of their direct applicability not only to recent human development but also to
historic, prehistoric and fossil studies of variation. Thus by comparing these
populations, I hope to increase understanding of the effects of climate on human
Suggested associations between human morphological variation and climatic
or environmental factors are as old as scientific thought, appearing as early as
Aristotle (Kennedy, 1976; Roberts, 1978). Even prior to Darwins articulation of the
concept of natural selection as a means for evolutionary adaptation, researchers
speculated on the influence of climatic variables, such as temperature and humidity,
in the appearance of racial attributes (Kennedy, 1976; Roberts, 1978). Based on
observations of existing variation, these early theories were post hoc and not
scientifically tested, but they demonstrate the antiquity of our interest in
understanding the ecogeographical patterning of morphology in humans.
In the early twentieth century studies began to appear which quantified
variation in human populations that were subject to shifts in environment. First
among these was Franz Boas study of anthropometric variation between immigrants
to the United States and their descendants and populations from their homeland
(1912). While many of his conclusions are questionable, the groundwork was laid
for future studies of migrant populations and their use in examining the relationship
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between the environment and morphological variation, which will be discussed
Prior to Boas work, principles about exactly how climate should affect
variation had already been established. In the nineteenth century two individuals
articulated what we now accept as rules of ecogeographical patterning. Bergmann
(1847 as translated in James, 1970) observed that variation of body size within a
species coincided with latitude, with larger variants occurring at higher latitudes and
smaller variants occurring closer to the equator. This variation, therefore, also
coincided with temperature. Bergmann also observed that there were modifications
apparent to this pattern, some of which were later articulated by Allen (1877).
Building on Bergmanns theory of size variation, Allen addressed variation in the
shape of an organism in relation to climate. He observed that the extremities of
organisms in a geographically dispersed taxon were longer for those found in the
tropics and were reduced in those from colder latitudes, invoking natural selection as
the most probable mechanism responsible.
Taken together these principles governing clinal variation can be viewed in
terms of thermodynamics. The size and shape of a body is influenced by two
different physiological functions heat production and heat loss. Ruff (1994)
eloquently uses the cylindrical model to describe these variants in body shape. If
the body is viewed as a cylinder, increases in volume (i.e., body mass) will result in
relatively less surface area per unit of volume, since volume increases at the rate of a
cube while area increases at the rate of a square. In the case of a homeothermic
organism, this results in greater heat production relative to heat dissipation, so an
increase in size (body mass) results in greater relative heat retention, an advantage in
a colder environment. Conversely, a reduction in volume will result in
proportionally greater surface area compared to volume i.e., relatively greater heat
dissipation a more appropriate body form in a tropical environment. While this
concept largely applies to Bergmanns rule regarding overall body size variation, it is
also applicable to the extremities of an organism. Changes in the height or length of
a limb will produce a different proportional volume, which when combined with the
entire body results in a change in shape. As limbs become shorter or longer, they
serve to change the relative surface area of a body, impacting heat dissipation.
Based on these principles, body form can be predicted for different geographical
areas, allowing researchers to test the validity of Bergmanns and Allens rules.
In the past, however, there has been some criticism of these rules of
ecogeographical patterning. Scholander (1955) points out the inconsistencies to
these rules when looking at arctic populations across various taxa and in essence
argues against any long-term adaptation in relation to climate. He asserts that
physiological adaptations are more likely to play a role and additionally suggests that
the cultural adaptations of humans in extreme climates would eliminate temperature
as a selective pressure (Scholander, 1955; 1956). Although the first criticism has
merit and is addressed below, the second is a recent development in human history
and is not supported by archaeological and fossil evidence.
In response to the first critique, Mayr (1956) argues that these
ecogeographical rules are meant to be applied to single or closely related species and
that is likely that at higher taxonomic levels they may not be observable. He goes
further to assert that physiological adaptations would not preclude morphological
adaptations and would be likely to coincide, since the process of natural selection
can result in multiple adaptations designed to solve the same problem. Ruff (1994)
also points out that although cultural adaptations may alleviate some of the stress
placed on a group by extreme temperatures, individuals would still be partially
subjected to them and it is these extremes that would create selective pressure for the
evolution of a particular body type.
Evidence of Ecogeographical Patterning
Bergmanns and Allens rules have been demonstrated multiple times in adult
populations through comparisons of anthropometric measurements such as stature,
relative sitting height, bi-iliac breadth, limb bone lengths and brachial and crural
indices (Schultz, 1937; Roberts, 1978; Trinkaus, 1981; Ruff, 1994; Holliday and
Ruff, 2001). Researchers have shown that populations found in colder climates are
more massive (reflecting Bergmanns Rule), have broader bodies and relatively
shorter limb segments, particularly the distal elements (reflecting Allens Rule),
while those groups from tropical regions tend to have relatively shorter and narrower
trunks as well as longer limb segments. The extremes of body shape are observed in
equatorial Africa and in the polar regions of North America and Eurasia (Roberts,
1978; Trinkaus, 1981; Ruff, 1994; Holliday and Ruff, 2001).
The factor that has largely been used as a causal link to body shape and size
is mean annual temperature (Trinkaus, 1981). However, other variables have
occasionally been used to describe the environment. Humidity is believed to play an
important role in the creation of tropical body forms, with wet climates producing
more linear, long-limbed bodies and dry climates providing less selective pressure
for these changes (Baker, 1960; James, 1970). Ruff (1994) used latitude rather than
temperature to differentiate populations in his large-scale comparison. Although
altitude would undoubtedly create variation within a small latitudinal range, latitude
was found to produce roughly the same results as mean annual temperature (Ruff,
Alternative Explanations for Selection in Body Form
In addition to variance due to climatic factors, there is some debate as to what
internal physiological mechanisms are responsible for clinal variation in body form.
Although generally attributed to natural selection, and therefore the result of genetic
adaptation (Allen, 1877; Holiday 1997a and b, 1999; Lim et al., 2000; Warren et al.,
2002), there is evidence that these patterns may result from developmental processes
(Weaver and Ingram, 1969; Reisenfield, 1973, 1981; Bogin and Rios, 2003).
Reisenfelds 1981 study of rodents suggests that exposure to a specific environment
(in this case, cold) during growth will produce the body types predicted by
Bergmann and Allen and that genetic adaptation is not necessary. Similar results
were demonstrated by Weaver and Ingram (1969) in a study of pigs where the
specimens subjected to colder environments were characterized by shorter tails and
stockier builds. In both studies, nutritional factors were controlled for as much as
possible, supporting the hypothesis that exposure to a certain climate during
development will create the body forms predicted by Bergmanns and Allens rules.
This follows Hulses (1960) suggestion that plasticity in development is selected for
and is the trait that allows organisms to live in different climatic zones rather than the
specific body shape or size.
Nutrition, and (in humans) the oft-coincident socio-economic status, may also
be a confounding variable in any attempt to study the relationship between body
form and climate. In some studies, nutrition has been shown to have some effect on
body form in humans (Ito, 1942; Benoist, 1975; Eveleth and Tanner, 1976, 1990;
Trinkaus, 1981; Martorell et ah, 1988; Bogin and Rios, 2003). Not surprisingly,
improved nutrition is correlated with increases in stature and is observed in various
populations worldwide as improvements in available health and nutrition have
become more widespread over the last 100 years (Eveleth and Tanner, 1990;
Katzmarzyk and Leonard, 1998). Several studies of immigrant populations to the
United States have found that while stature increases, often within a single
generation, body proportions usually remain similar to the original population and
the increase in stature is usually attributed to better health status of the immigrant
groups (Ito, 1942; Benoist, 1975; Eveleth and Tanner, 1976, 1990; Trinkaus, 1981;
Martorell et al., 1988).
However, there are studies of Japanese and Mayan-Americans, demonstrating
a secular trend of both increased stature and relative leg-length in both native and
migrant groups (Ito, 1942; Froelich, 1970; Bogin and Rios, 2003). As discussed
above, the pattern of increased stature has recently been observed worldwide and is
not unique in itself (Katzmarzyk and Leonard, 1998; Jantz and Jantz, 1999). Several
studies demonstrate little change in relative body proportions even with an increase
in stature (Benoist, 1975; Eveleth and Tanner, 1976, 1990; Trinkaus, 1981; Martorell
et al., 1988). However, the Japanese exhibit a change in body form (Tanner et al.,
1982). Asians are broadly characterized by shorter stature, but a higher sitting height
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ratio when compared to groups of European and African descent (Ito, 1942; Eveleth
and Tanner, 1976) in other words, relatively short legs. While recent groups
demonstrate the same secular trend for increased stature seen in several other
populations, the sitting height/stature ratio has also shifted to reflect a larger
proportion of stature being comprised of leg length (Tanner et al., 1982). Despite
this, the Japanese still currently reflect a body-form more similar to Asian
populations than to other groups. A similar pattern is evident in Bogin and Rios
2003 study of Mayans in Guatemala and the U.S. Again, while sitting height to
height ratios are lower for those of Mayan affinity living in the United States than
those in Guatemala, they are still intermediate between the Guatemalans and U.S.
residents of European descent. This suggests that while body proportions may be
primarily determined by heredity, nutritional status may have an effect on them as
In the multiple studies of body form differences between Americans of
African and European background, an interesting pattern is evident which is related
to the suggestions that nutrition and developmental processes may account for
differences in body form (Eveleth and Tanner, 1976; Trinkaus, 1981; Steele and
Mattox, 1987; Martorell et al., 1988; Holliday and Falsetti, 1999; Bogin and Rios,
2003). In these studies, African-Americans are shown to possess a body form
reflective of other tropical groups from the Old World that of relatively long legs
compared to sitting height or trunk length. While there is the possibility that
differences may have existed in socio-economic status between these groups, this
seems unlikely to have any impact on the results. Poorer nutrition and other impacts
from low socio-economic status are likely to result in retarded growth of the body
and limbs and may, if anything, serve to lessen the differences in body form between
the groups (Katzmarzyk and Leonard, 1998). Additionally, climatic variables in the
U.S. are more temperate than those of Africa from which the reference samples were
taken (Trinkaus, 1981; Holliday and Falsetti, 1999). As with nutritional factors, the
new environment in the U.S. would likely lessen any differences in body proportions
between Americans of African and European descent. Subsequently, these studies
suggest that while body size may be affected by immediate response to conditions,
body shape at least has a strong genetic component.
Climatic Adaptation in Children
One way to examine the question of causality in variation is to examine
juveniles, but few studies have attempted to quantify differences in body form of
children from ecogeographically disparate populations with a specific reference to
climate. Instead, studies examining growth of post-cranial measurements in children
reflective of body shape and size have tended to focus on differences in rates and
timing of growth among groups (Eveleth and Tanner, 1976, 1990; Humphrey, 1998)
- 13 -
or secular changes in body form within populations (Jantz and Owsley, 1984a; Bogin
and Rios, 2003).
A large number of studies have focused on the differences between racial
groups. While these categories are problematic, they do often coincide with
ecogeographically disparate groups and are useful if cautiously interpreted. The
most thorough of these are the compilations of Eveleth and Tanner (1976, 1990) as
part of the International Biological Programme. Eveleth and Tanner
comprehensively described growth patterns of populations from Europe, Asia,
Africa, Australia, the Middle East and descendent populations in the American
continents, discussed further in the following section. They also examined rates of
maturity, measures of size and some body proportions. While some association
between climate and body form was assessed, the variables used tend to focus more
on size in the form of weight and height measures. The results of their research
support ecogeographical patterning of body form in adults and that differences are
also present in children. However, these assessments are sometimes based on
generalized categories of Europeans, Africans and Asians. While providing useful
baseline information, these groupings are subject to internal variation as well.
Cheng et al., (1996) in an anthropometric study of children from Hong Kong,
found that Chinese children do exhibit different body proportions (in the form of
height to arm span and height to sitting height ratios) from Caucasians and
Africans/African-Americans. These results corroborate studies of Asians mentioned
earlier that demonstrate the relatively shorter limbs characterized by those groups.
A study by yEdnyak (1976) comparing growth in indigenous Alaskans to
Americans of European descent examines the variation in long bone lengths between
these groups. Comparisons to a modem reference sample indicated that the
characteristically shorter limb bones, particularly distal segments, found in Arctic
populations are present in early childhood.
There has also been research demonstrating that differences in body
proportions between differing racial groups are apparent in fetuses and newborns
(Schultz, 1923; Lim et al., 2000; Warren et al., 2002). The study by Lim et al.
(2000) compares crown-heel length in newborns (comparable to stature) against
femoral length. In this study, they demonstrated that for a given height, there was a
significant difference between those identified1 as Indian and those that were either
Chinese or Malay. The research by Warren et al. (2002) and Schultz (1923) supports
the results of Lim et al. (2000) in their findings that fetal proportions reflected those
of adult members of the same population. Although these studies do not address
issues of climatic adaptation, they demonstrate that some body shape differences
between populations are apparent at birth, which suggests that differing body
proportions are at least in part the result of long-term genetic changes rather than
1 Method of determining ethnic affiliation was not given by the authors.
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As mentioned in the previous section, the rate at which children grow has
also been shown to vary by population (Eveleth and Tanner, 1976, 1990; Merchant
and Ubelaker, 1977; Humphrey, 2003). While size and shape differences among
populations may be present in children as well as adults, variation in rates of growth
may influence any assessment of populational differences in shape. Since the tempo
of growth does not have an effect on the final size attainment (Eveleth and Tanner,
1976, 1990), comparing children from different populations at the same age may
result in patterns that are different from comparisons of adults from different
populations. For example, the studies complied by Eveleth and Tanner (1976, 1990)
report that African and African-American populations mature at a faster rate than
children of European descent in skeletal development and final height attainment.
Asian populations are found to mature at an even faster rate than the African groups
(Eveleth and Tanner, 1976, 1990). Though nutritional levels can have an effect on
an individuals growth trajectory (Moore et al., 1986), skeletal maturation is believed
to have a strong genetic component (Eveleth, 1986).
In skeletal collections, one way of examining maturation rates is to compare
estimates of skeletal age to dental age. Research by Moore et al. (1986) on
maturation rates of a Sudanese Nubian population from Kulubnarti found that the
inhabitants experienced a reduction in the rate of skeletal maturation compared to
modem reference samples of European descent.
A similar pattern is reported by Johnston (1962) for a large collection of
juvenile skeletons from the Indian Knoll site in Kentucky. In this study, the
individual long bones are analyzed and found to fall below averages for Caucasian
children in the U.S., indicating a slower rate of growth for the Native Americans at
Indian Knoll. However, the results could also be the product of overall differences
in stature between groups. To eliminate variation in stature as a confounding
variable, Lovejoy et al. (1990) did a similar comparison with a population of Native
Americans from the Libben site, but analyzed bone lengths as a percentage of final
adult attainment. Their results suggest that growth rates are similar between the
Libben group and comparative Euro American groups (Lovejoy et al., 1990).
Steyn and Hennebergs (1996) comparison of the long bone data for the
South African K2 site to a modem group of children from the same region as well as
the Libben and Indian Knoll Native American populations, the Eskimo/Aleut
assessed by YEdnyak (1976) and a population from Altenerding, Germany
(Sundick, 1978) found only subtle differences between groups in the tempo of
growth of long bones. Sundicks own research (1978) comparing the German
population with that from Indian Knoll demonstrated that rates of growth were
similar at least until puberty. However, Humphrey (2003) found that all of the above
- 17 -
populations as well as several others2 faltered in femoral growth after approximately
six months of age when measured as a percentage of adult attainment against a
modem Caucasian reference sample.
Limb bones within an individual also vary in growth rates (Anderson and
Green, 1948; Smith and Buschang, 2004). Studies indicate that segments of each
limb do not follow the same trajectory in length measurements and that proximal
segments, being longer, demonstrate a greater velocity than distal segments
(Ulijaszek et al., 1998; Smith and Buschang, 2004). The same pattern is true for the
lower limb compared to the upper limb, as the femur and tibia are longer than the
humerus and radius (Ulijaszek et al., 1998; Smith and Buschang, 2004). Differences
in rates also occur between males and females, but these are not usually pronounced
until adolescence (Anderson and Green, 1948; Ulijaszek et al., 1998; Ruff, 2003;
Smith and Buschang, 2004).
An allometric analysis of the variation between upper and lower limbs by
Jungers et al. (1988) using the Arikara collection found that the lower limb was
characterized by positive allometric growth, while the upper limb showed negative
allometric growth. These results coincide with similar findings using modem
Caucasian samples (Ulijaszek et al., 1998; Smith and Buschang, 2004) indicating
that this is not variable between populations. Jantz and Owsley (1984a), in an earlier
2 This pattern includes a sample from Khok Phanom Di, Thailand, which is discussed in later
- 18 -
study with the Arikara, found a similar pattern but discovered that proportional
changes in the lower limb (the relationship of distal to proximal segments) were not
consistent among various sites for the collection. This variation appeared to follow a
temporal pattern with earlier sites possessing relatively shorter tibiae.
The rate of growth does not remain consistent throughout childhood, as
demonstrated by Hummert and Van Gerven (1983). In their analysis of the
Kulubnarti, Nubia collection, they found that growth in all limb segments was most
rapid from infancy to approximately 2 'A years of age and then slowed until the
adolescent growth spurt began. While the rate of growth for each bone followed the
above-mentioned patterns (lower faster than upper), all segments accelerated and
decelerated in rate at the same ages. Armelagos et al. (1972) found a similar pattern
for the femur, but also detected a slight mid-childhood growth spurt, although this
may be the result of the sample including multiple sites from Sudanese Nubia.
All of the research presented above suggests considerations for examining the
development of body proportions in children as they grow. It is evident that
variation may be the result of additional factors besides climatic adaptation.
The primary goal of this study it to examine whether or not body proportions
of adults from ecogeographically disparate populations are reflected in the juvenile
specimens for each population. If Bergmanns and Allens rules can be
demonstrated to characterize differences in adult populations, then the question of
interest is if and how these proportions are manifested in children. While some
studies have completed analyses for small age ranges such as fetuses (discussed
above), there has been very little published that examines relative body shape across
all age groups in relation to populational differences (Ruff et al., 2002). Conclusions
drawn about body shape variables based on a small age range for a population are
useful in providing a theoretical basis for broader studies of the relationship between
body proportions and climate throughout development.
Previous studies by Lim et al. (2000), Ruff et al. (2002), and Warren et al.
(2002) demonstrate a patterned relationship between children and adults from a
given population when compared to other groups. Following that evidence, the main
prediction of this study is that juvenile samples will reflect the body shape of the
adults within a population from birth and throughout development. Variables used in
this study include limb segments and indices and are discussed further in the
Brachial and Crural Indices
Brachial and crural indices are useful measures of body shape since they
quantify the relative size of limb bones. They are useful for several reasons. First
they quantify limb proportionality in a single measure. Additionally, while
differences in absolute size among individuals may also be reflected in proportion
ratios, the distal measurements are to some extent standardized relative to the
proximal measurements (Trinkaus, 1981). Lastly, the component bones are usually
available for skeletal populations, whereas other measures such as body mass and
height are difficult if not impossible to ascertain. Therefore, the use of brachial and
crural indices to quantify body shape is an appropriate method for this type of study.
Specific Questions and Predictions
For this study, the main prediction is that brachial and crural indices in
children from the collections discussed in the next chapter will reflect those of adults
from the same population. Based on earlier research, this is a logical assumption
(Lim et al., 2000; Ruff et al., 2002; Warren, et al., 2002). The following questions
- 21 -
are designed to address the issues associated with the primary prediction of the
1. Do the adult brachial and crural indices differ significantly among the
three sample populations of this study? To examine this, the level of
variation in brachial and crural indices present among adult reference
samples will be established and a determination must be made of
whether variation between groups coincides with climate. The
potential of other variables such as sexual dimorphism or nutritional
level to influence the results will be examined and if possible
addressed for the juveniles as well.
2. Are the brachial and crural indices of juveniles within a population
equivalent to the adults of the same populations? The analyses here
will determine to what extent juvenile brachial and crural indices
reflect those of the adults from the same sample and assess any
variation among the juveniles. This will be examined for the groups
as a whole as well as across various age ranges.
3. What mechanisms are likely responsible for any variation among the
juvenile samples? Variation could be the result of growth rate
differences or environmental influences other than climate, such as
4. How do the results reflect previous research? A comparison of the
populations from the current study will be compared to available
published data to provide a better understanding of how these
populations fit into the broader evidence for ecogeographical
patterning in morphology among humans.
MATERIALS AND METHODS
In this study, three samples representing a variety of climates are analyzed.
The skeletal collections used in this study were selected for several reasons -
antiquity of the sites/collections, geographical/climatic variation, large number of
juveniles, and measurable long bones. Archaeological samples are most appropriate
for this study for several reasons. As discussed above, present day groups are likely
to demonstrate the secular trends of increased stature and size observed in many
Western populations due to improved nutrition (Katzmarzyk and Leonard, 1998;
Jantz and Jantz, 1999). While this has not been shown to correspond to a change in
limb proportions in several of the studies discussed in earlier chapters, the exception
of recent Japanese is notable (Froelich, 1970). Additionally, recent technological
advances such as air conditioning may lessen the selective pressure of temperature
on the body in recent generations (Scholander, 1955), but will be minimized in
archaeological populations. Furthermore, older populations are likely to have been
freer of admixture with colonizing groups, thereby minimizing the potential
influences of gene flow on phenotype.
Two collections fulfdling these criteria were examined and measured by the
author. The Kulubnarti collection from Sudanese Nubia housed at the University of
- 24 -
Colorado at Boulder and a collection of Aleutians and mainland Alaskan natives
housed at the National Museum of Natural History Smithsonian Institute provided
samples of warm and cold adapted populations, respectively. A third collection with
published data also met the requirements. Individual measurements of an
archaeological population from the Khok Phanom Di site in Thailand, published by
Tayles (1999), were also analyzed and compared with the previous two populations.
Though often referred to as Arctic, the specimens from the National
Museum of Natural History Smithsonian Institute collection are almost all from
sites below the Arctic Circle (Smithsonian database). Sites ranged from the western
Aleutian Islands to the southwestern and western regions of Alaska, with a few
specimens from the Alaskan site of Barrow located on the northern border of the
state (geographic mean latitude ~ 64N). Although there are many cultural groups
represented throughout this area, the region is broadly split between those inhabiting
the Aleutian Islands and those inhabiting the mainland of Alaska. There has been a
lot of speculation about the route used in peopling this area, but recent research
(Ousley, 1995) suggests that the Aleutians were the earlier inhabitants and were
pushed into the islands by subsequent waves of settlement into the mainland.
Although there are some cultural and genetic differences among these various groups
as a result of these multiple waves of migration across the Bering Strait, they are still
thought to be genetically more similar to each other than to other groups and
essentially inhabit the same climatic zone (Hrdlicka, 1945; Ousley, 1995; Sheilds et
al., 1993). For this reason, they are treated as a single population in comparison to
the other geographic groups for most analyses here. Flowever, analyses were carried
out with the two adult subpopulations separated to determine if any differences in
limb proportionality exist between them.
For the Aleut/Eskimo population, 80 juvenile individuals had at least one
long bone that was measurable, though some of these did not possess a
humerus/radius or femur/tibia pair to allow either brachial or crural index to be
calculated. However, the vast majority had enough material to calculate at least one
such index (see Table 4.1 for number of measurements). Additionally, 56 adults
were measured for use as a reference sample with approximately half coming from
the Aleutian Islands and the other half from the mainland.
Ages for the individuals were based on dental eruption and were in most
cases already established by the researchers at the National Museum of Natural
History. Although radiographic analyses were done on most specimens, this was
done after age had already been determined (D. Hunt, pers. communication). In some
instances, no age was indicated for a specimen other than the designation of infant,
child or adolescent. In these cases, dental eruption, following the standards
established by Ubelaker (1989) and reprinted in White (1991), was used by the
author in the current study to estimate the dental age. Because of the methods used,
dental ages were recorded as ranges rather than precise years. However, for
statistical analyses, the midpoint of the range was used. Although this is not ideal,
since age categories were primarily used in the analyses and not individual ages, it is
unlikely that this method would have a large influence on the results.
The collection from the eastern Africa medieval site of Kulubnarti is divided
into two cemetery groups, one from the mainland and the other from an adjacent
island on the west bank of the Nile River. The island cemetery was inhabited during
an earlier Christian period (550-750 A.D.) and the mainland cemetery was inhabited
primarily during the late and terminal Christian periods (750-1450 A.D.), though
there may have been some overlap with the earlier period (Hummert and Van
Gerven, 1983). Because of the sites location between different regional or ethnic
groups, the inhabitants of this area are considered to have been a mixture of both
Egyptian and sub-Sahara African populations (Carlson and Van Gerven, 1979;
Hummert and Van Gerven, 1983).
The populations consist of 218 individuals from the island cemetery, part of
the early Christian period, and 188 from the mainland cemetery and late Christian
period (Hummert and Van Gerven, 1983). Of these cemeteries, 110 juveniles from
the island and 47 from the mainland had at least one paired set of long bones. A few
additional individuals had long bones, but not a paired set and were only included for
calculating means for each long bone. While all limb bones measurements were
taken by the author, dental ages previously determined and recorded with the
collection were used for this project. The juveniles range from six months in utero
to 12 years old. For a comparative adult sample, 53 adults were measured to achieve
a minimum of fifteen crural and fifteen brachial indices from each cemetery (see
Previous studies of the Kulubnarti collection have demonstrated that the
island population exhibited signs of environmental stress that impacted growth when
compared to the more recent mainland inhabitants (Hummert and Van Gerven, 1983;
Albert and Greene, 1999). This provides the current research project with a way to
possibly test for the impact of environmental variables on relative limb proportions,
since these two populations are known to be genetically similar (Hummert and Van
Gerven, 1983) and to have inhabited the same warm climate (latitude 21N). If
there are anthropometric differences between the two subgroups within the Nubian
population, they may be attributed to the different levels of nutrition.
Khok Phanom Di
The site at Khok Phanom Di in coastal Thailand provides a large collection of
juvenile skeletons with recorded individual measurements, primarily infants, and is
dated to approximately 2000-1500 BC (Tayles, 1999). Khok Phanom Di is situated
in an area characterized by rivers and swampland and can be characterized as having
a warm and humid climate (latitude 13N). Archaeological evidence suggests that
the inhabitants had access to abundant resources and therefore were not likely to be
under any heavy environmental stress. The collection is well preserved and of the
154 individuals, 81 are children age 12 and younger with intact long bones measured
and recorded by Tayles (1999). Tayles (1999) used a variety of indicators to
determine the age of each skeleton including dental calcification and eruption,
skeletal maturity and diaphyseal length. Many of the juveniles did not have a pair of
long bones from either the upper or lower limb, bringing the total sample size for
brachial and crural measurements down to 56 individuals, but several had unpaired
long bone measurements. All available measurements for given adults were
included (see Table 4.1).
A previous comparative study of stature using limb length as a predictor for
the adults indicate that the Khok Phanom Di population was shorter than other
prehistoric Thai groups, though this was only statistically significant for the males
(Tayles, 1999). An assessment by Tayles (1999) of limb proportions using brachial
and crural indices for adults indicates that the Khok Phanom Di population is in the
higher range compared to worldwide means, reflecting a tropically adapted body
form (Allen, 1877; Tayles, 1999).
Table 4.1 Number of measurements available for sample populations.
Population #of Individuals # of Measurements Recorded
Humerus Radius Brachial Index Femur Tibia Crural Index
Alaska/ Aleutian Isl Adults 56 48 48 48 53 53 53
Juveniles 73 56 57 44 55 51 44
Kulubnarti, Nubia Adults 53 48 48 48 49 49 49
Juveniles 164 162 156 153 150 121 108
Khok Phanom Di, Thailand Adults 50 43 43 43 36 36 36
Juveniles 81 65 43 33 63 57 47
Additional Populations with Published Data
Means for long bone lengths have been published for several other
archaeological sites containing juveniles and are detailed below. Although ratios
derived from means are not equivalent to means of ratios derived from individual
measurements (Ruff et al., 2002), these data provide useful supplemental information
about climatic adaptation and are included in the discussion of this study.
The German site of Altenerding is located in Bavaria near the city of Munich
(latitude 48N) and is dated to the 6th or 7th century AD (Sundick, 1978). The
population is of European ancestry and dental eruption and formation were used to
determine the ages of the 82 juvenile skeletons. Sundick recorded the data in dental
stages that correspond to increments ranging from 6 to 30 months (1978).
Measurements included in the published article for all long bones were maximum,
minimum and mean diaphyseal length and the standard deviation with comparative
adult data. The measured collection consisted of 36 individuals with postcranial
elements, but the number of measurements varied by bone.
The Arikara collection, housed at the National Museum of Natural Science
and the University of Tennessee, consisted of several different tribes from the
Mobridge site (latitude 37N) in South Dakota (Merchant and Ubelaker, 1977;
Jantz and Owsley, 1984a; Jantz and Owsley, 1984b). The collection is dated to after
1300 A.D (Jantz and Owsley, 1984a; Jantz and Owsley, 1984b). The Arikara are
thought to have migrated to South Dakota from the central and possibly Southern
Plains area, a more temperate region (Jantz and Owsley, 1984b). Merchant and
Ubelaker (1977) assigned a mean age corresponding to a year plus/minus 6 months,
with the first age group being birth to .5 years old and yearly increments up to adult
following. The ages were determined by assigning a dental development rating for
several teeth (see Merchant and Ubelaker, 1977, for more detail discussion of aging
methods). Mean values for long bones were reported for the 193 individuals used
(Merchant and Ubelaker, 1977).
The pre-agricultural Kentucky site of Indian Knoll (latitude 46N) dates to
about 5000 BP and consists of 165 juvenile skeletons aged only from birth to 5 'A
years old. Analyses of the juvenile skeletal remains were published by Johnson
(1962), who used dental and osseous criteria for aging. Mean values for each limb
bone and comparative rates of growth are included. Specimens were grouped in one-
year increments except those under the age of one, which were separated into fetuses
and newborns. Adult means for this collection are not included by Johnson, but can
be found in Sundick (1978), who also studied this collection.
K2, South Africa
Archaeological populations for sub-Saharan Africa are scarce, but the K2 site
does contain juveniles (Steyn and Henneberg, 1996; Humphrey, 2003). Located in
the Northern Transvaal region of southern Africa (latitude 24S), the K2 site was
inhabited by people judged to be relatively healthy and engaged in pastoralism and
economic trade, suggesting that nutritional stress was unlikely. Of the 106
individuals excavated in the area, only 45 juveniles could be accurately aged using
dentition and a mention is made that 44 possess limb bones, although two of these
may have been subject to chronic disease (Steyn and Henneberg, 1996). Individual
long bone lengths are not given, but mean values for each of the six limb bones are
listed according to age ranges. Specimens are grouped in one-year increments over
the age of six months, while those under six months are divided into fetuses and
newborns (Steyn and Henneberg, 1996).
Maximum diaphyseal lengths for the humerus, radius, ulna, femur and tibia
were measured using an osteometric board for the Kulubnarti and Aleut/Alaskan
juvenile specimens. Measurement of the femur was taken as maximum length to
correspond to the already published data. Long bones with fused or attached
epiphyses were not included for measurement among the juveniles to ensure
consistency in comparisons. The fibula was not included because of the challenges
of correctly siding the bone in juveniles with unfused epiphyses. All measurements
recorded for the Khok Phanom Di site by Tayles (1999) were maximum diaphyseal
lengths. For the adults, all measurements include epiphyses.
As mentioned in the above sections, some specimens with measurable long
bones did not have a humeral-radial or femoral-tibial paired set. Because of the small
sample sizes for juveniles as a result of age stratification, these unpaired bones were
used in the analyses of limb segments, but not in the analyses of indices. Only
paired long bones were used for analyses of adults, since a greater number of
specimens with humeral-radial or femoral-tibial pairs were available. The right side
limb bones were used when possible, but to increase the sample size, the left side of
an individual was used if the right had missing data. This determination was made
due to a previous study of the Nubian collection that made the left side lower limb
bones unmeasurable for the present project.
Adults used here ranged in age from 20 to 45 years of age. Ages for adults
were previously determined for each collection and used here. The juveniles
included in the Kulubnarti and Alaska/Aleutian Island samples range in age from
birth to about 12 years in age. The published research sometimes included
adolescent data, but only those 12 years and under were included here. After this
age, it is likely that sex differences in the timing of the adolescent growth spurt
would skew results when grouped as a whole (Anderson and Green, 1948; Johnston
and Zimmer, 1989; Smith and Buschang, 2004). Since sex determinations are
generally not available for younger individuals due to the difficulty in discerning
such differences, the juvenile populations are grouped all together.
Ages were recorded for juvenile individuals, but they were also assigned to
one of 8 age groups to allow comparisons. Although this method is common in the
literature (yEdnyak, 1976; Sundick, 1978; Jantz and Owsley, 1984a; Lovejoy et al.,
1990), the size of the age cohorts is not standard. In this study, age groups were
divided into 2-year increments starting with 2.5 years of age (given in Table 4.2).
Age groups for younger specimens were intentionally divided somewhat differently.
Fetal specimens and those designated as newborn (0 years old) were grouped
together following research by Lim et al. (2000) and Warren et al. (2002). This
research indicates that such young juveniles that have not been subjected to any
environmental stressors (other than those inflicted in the womb) are reflective of the
adults from their population in body proportions. This will allow a similar
comparison with the populations in this study. For the ages between birth and 2.5
years, groups smaller than 2 years were used consisting of fetuses, newborns, and
those under 2 1/2 years of age. This trend is also found in much of the literature and
is reflective of the rapid growth seen in humans at this young age (Eveleth and
Tanner, 1976). The determinations of age groups were made to balance the
considerations of sample distribution and comparability with existing research.
Table 4.2 Number of measurements for juveniles available by population and age category.
Number of Measurements Available by Age Group
Population Measurement Age Group 1 Fetal Oy Age Group 2 0.1 1.5y Age Group 3 1.6- 2.5y Age Group 4 2.6 4.5y Age Group 5 4.6 6.5y Age Group 6 6.6 8.5y Age Group 7 8.6- 10.5y Age Group 8 10.6- 11.5y
Kulubnarti, Brachial Index 12 58 11 58 58 19 28 23
Nubia Crural Index 2 21 4 29 26 8 11 7
Humerus 15 62 12 65 62 23 29 25
Radius 13 66 11 62 59 19 28 23
Femur 11 54 10 62 48 14 21 16
Tibia 4 27 4 32 26 9 12 7
Alaska/ Brachial Index 2 9 4 9 16 6 7 5
Aleutian Islands Crural Index 2 10 7 14 21 3 6 7
Humerus 3 11 8 15 25 6 8 8
Radius 2 12 7 13 17 8 16 10
Femur 2 14 10 19 27 4 10 7
Tibia 4 11 7 17 24 4 9 9
Khok Brachial Index 29 8 2 0 0 3 2 2
Phanom Di, Crural Index 48 8 4 0 1 3 0 4
Thailand Humerus 56 23 2 1 2 4 4 3
Radius 38 11 2 0 1 3 3 8
Femur 63 17 6 1 1 4 2 6
Tibia 56 14 4 1 1 3 1 6
Data analyses were carried out using the statistical software SPSS vl4.
Analyses of variance and Scheffe tests for significant difference of means were used
to determine if any differences between populations and among age groups existed.
A t-test for independent samples was used to determine if sexual dimorphism existed
between adults from the same population and if nutrition could be a significant factor
within the Nubian population. A p-value of less than 0.05 was considered to indicate
a significant difference of means and is designated with an asterisk in all tables.
In some cases, a population did not have any specimens for a certain
measurement within a particular age group. In these cases, no statistically significant
differences could be determined. However, descriptive statistics were also used to
make inferences about the collections.
The statistical analyses of the Kulubnarti, Alaskan/Aleut and Khok Phanom
Di collection produced several expected results. Generally, the warm climate
populations (Kulubnarti and Khok Phanom Di) exhibited higher brachial and crural
indices than the cold-climate Alaska/Aleutian Island population. However there were
some important findings that did not strictly follow expectations, particularly in the
juveniles. To understand to populational characteristics, the results from the adult
samples are enumerated below, followed by the juvenile samples.
For adult long bones, the results conform well to research detailed in earlier
chapters. Nubians possess the longest means for humeri, radii, tibiae, and femora,
while the Thai are intermediate and the Alaskan/Aleutians are the shortest for all
bones. Figure 5.1 depicts the mean values for each limb bone for each population
(grouped by bone). Given Tayles (1999) research that suggests that the Khok
Phanom Di inhabitants were short in stature, it is not surprising that they exhibit
shorter limb segments than the Nubian specimens, despite being from a lower
Adult Mean Values
Khok Phanom Di, Thailand
Figure 5.1 Mean Values for Adult Long Bones.
However, mean values for the brachial indices indicate that the population
from the Khok Phanom Di site in Thailand have the highest index at 80.47 followed
by those from Kulubnarti, Nubia and then native Alaskan/Aleutian Islanders with the
lowest. For the crural index, the Nubians have the highest mean (86.25) followed by
the Thai population and then the Alaskan/Aleutian group with the lowest ratio
(Figure 5.2). Table 5.1 lists the mean values for all three populations along with
Adult Mean Values
Kulubnarti, Nubia Alaska/Aleutian Khok Phanom Di,
Figure 5.2 Mean Values for Adult Indices.
Using an Analysis of Variance and a Scheffe test for difference of means, all
three populations differed significantly from each other in brachial and crural
indices. Table 5.2 lists p-values for adults with significant results indicated by an
asterisk (*). The contribution of each limb segment to the brachial index can account
for the result that the Thai population has the highest brachial index, though it is
intermediate for each segment. For example, the Thai are much closer to the
Alaskan/Aleutian group for the humerus and closer to the Nubians for the radius. In
other words, they are characterized by a much shorter humerus compared to radius,
explaining the observed high brachial index. This is consistent with the findings by
Tayles (1999). The crural indices are not remarkable as they follow the same pattern
as the limb bone values.
Table 5.1 Descriptive statistics for adults by population.
Population Measurement N Minimum Maximum Mean Std. Deviation
Kulubnarti, Brachial Index 48 73.45 85.08 78.86 2.191
Nubia Crural Index 49 80.97 90.43 86.25 2.282
Humerus 48 262.00 347.50 308.81 18.185
Radius 48 211.00 275.50 243.55 16.106
Femur 49 372.50 475.50 429.78 26.013
Tibia 49 318.00 414.00 370.61 23.304
Alaska/ Brachial Index 48 67.74 81.19 73.84 2.806
Aleutian Crural Index 53 74.12 85.79 80.35 2.419
Islands Humerus 48 266.50 360.00 295.10 19.327
Radius 48 188.00 260.00 217.99 17.654
Femur 53 362.50 486.00 407.04 25.646
Tibia 53 274.00 389.00 327.13 23.674
Khok Brachial Index 43 75.69 88.10 80.47 2.760
Phanont Di, Thailand Crural Index 36 79.95 88.66 84.54 2.079
Humerus 43 255.00 328.00 297.02 17.130
Radius 43 202.00 275.00 239.07 17.059
Femur 36 380.00 459.00 420.36 21.947
Tibia 36 315.00 391.00 355.36 20.550
Table 5.2 Comparison of adult mean indices, ANOVA results
Adult Population Comparison of Brachial Indices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Overall difference between groups, p-value Nubia <0.001* Alaskan/Aleut <0.001* Thai 0.015* <0.001*
Adult Population Comparison of Crural In dices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Overall difference between groups, p-value Nubian <0.001* Alaskan/Aleut <0.001* Thai 0.004* <0.001*
The populations are not all significantly different in mean values for each
component bone (Table 5.3). The Nubians are significantly different from the
Alaskan/Aleutian and Thai populations for the humerus, but the Aleut/Alaskans and
Thai are not significantly different from each other. For the radius, the Nubians and
Thai are not significantly different, but the Alaskan/Aleutian group is significantly
different from both. Given the results discussed above for brachial index values, this
is not unexpected. For the femur, the results are similar to those for the radius with
the Nubians and Thai being significantly different from the Alaskan/Aleutians, but
not from each other. The tibia is the only bone to be significantly different for all
Table 5.3 Comparison of adult mean values by limb bone, ANOVA results
Adult Population Comparison for Humerus, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Nubian Alaskan/Aleut Thai <0.001* 0.010* 0.882
Khok Phanom Di, Thailand Overall difference between groups, p-value 0.001*
Adult Population Comparison for Radius, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Nubian Alaskan/Aleut Thai <0.001* 0.456 <0.001*
Khok Phanom Di, Thailand Overall difference between groups, p-value <0.001*
Adult Population Comparison for Femur, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Nubian Alaskan/Aleut Thai <0.001* 0.23 0.050*
Overall difference between groups, p-value <0.001*
Adult Population Comparison for Tibia, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Nubian Alaskan/Aleut Thai <0.001* <0.011* <0.001*
Khok Phanom Di, Thailand Overall difference between groups, p-value <0.001*
Within Population Variation
As discussed in the materials section previously, the populations from
Kulubnarti, Nubia and Alaska/Aleutian Islands can be subdivided into sub-
populations by cemetery and time period for the Nubian group and by ethnic
affiliation for the Alaskan/Aleut group. To determine if these sub-groups have any
relevance to the present study, an analysis of variance was carried out for the
subpopulations (p-values are listed in Table 5.4). The two Nubian groups were not
significantly different from each other for either brachial or crural indices and both
were still significantly different from the Alaskan/Aleut subgroups. The same was
true for the Alaskan/Aleut population the two subgroups were not significantly
different from each other. Additionally, the Arctic subpopulations were significantly
different from both Nubian groups and from the Thai population.
However, there were some interesting results for the Thai population when
compared to the Nubian subgroups. For brachial indices, the Nubian S cemetery was
not significantly different from the Thai group, exhibiting higher values for both the
index and each upper limb bone than the R cemetery (Table 5.5). Although the
Nubian R cemetery is not significantly different from the Thai for the brachial index
either (p = 0.051), it is very nearly so. Since the population from the S cemetery is
believed to have been under greater nutritional stress than individuals from the R
cemetery (Hummert and Van Gerven, 1983; Albert and Greene, 1999) and the Thai
group is believed to have benefited from abundant food resources (Tayles, 1999), the
results suggest that nutrition may not have an impact on upper limb bones. One
would expect nutritional stress to result in shorter limbs (Katsmarzyk and Leonard,
1998; Bogin and Rios, 2003), but that is not the pattern observed here.
For crural indices, the Nubian R cemetery and Thai were not significantly
different (p = 0.150), but the Nubian S cemetery is significantly different from the
Thai. It is interesting that the lower limbs show different patterns between the two
Nubian groups in relation to the Thai. However, the relationships among groups here
are likely to be attributed to the crural index values being lower for the Thai, since
the R cemetery is characterized by shorter lower limb bones than the S cemetery as is
the case with the upper limbs.
The differences between the Nubian groups are noteworthy results and will
be discussed further in the next chapter because of the implications for nutritional
considerations. However, the Nubian and Alaskan/Aleut sub-populations are treated
as whole groups for the broad juvenile analysis, since no significant differences were
found to exist within each population. With the juvenile samples already divided
into smaller subgroups (see Table 4.2), further dividing them could render any
statistical analysis meaningless.
Table 5.4 Comparison of adult indices by sub-population, ANOVA results
Adult Sub-Population Comparison of Brachial Indices, p-values
Nubia Island Cemetery S Nubia Mainland Cemetery R Alaska Aleutian Islands Thai Nubian S Nubian R 0.924 Alaskan <0.001 <0.001 Aleut <0.001 <0.001 0.623 Thai 0.583 0.027 <0.001 <0.001
Overall difference between groups, p-value <0.001
Adult Sub-Population Comparison of Crural Indices, p-values
Nubian S Nubian R Alaskan Aleut Thai
Nubia Island Cemetery S 0.905 <0.001 <0.001 0.052
Nubia Mainland Cemetery R - <0.001 <0.001 0.011
Alaska - 0.867 <0.001
Aleutian Islands - <0.001
Overall difference between groups, p-value <0.001
Table 5.5 Descriptive Statistics of Adult Subpopulations
Population Measurement N Mean
Kulubnarti, Nubia Brachial Index 30 78.59
R (Mainland) Cemetery Crural Index 31 86.00
Humerus 30 306.60
Radius 30 240.92
Femur 31 426.54
Tibia 31 366.68
Kulubnarti, Nubia Brachial Index 18 79.31
S (Island) Cemetery Crural Index 18 86.68
Humerus 18 312.50
Radius 18 247.93
Femur 18 435.33
Tibia 18 377.39
Alaska (Mainland) Brachial Index 23 72.79
Crural Index 26 79.95
Humerus 23 289.72
Radius 23 210.99
Femur 26 402.40
Tibia 26 321.88
Aleutian Islands Brachial Index 25 74.80
Crural Index 27 80.74
Humerus 25 300.05
Radius 25 224.42
Femur 27 411.51
Tibia 27 332.19
Khok Phanom Di, Thailand Brachial Index 43 80.47
Crural Index 36 84.54
Humerus 43 297.02
Radius 43 239.07
Femur 36 420.36
Tibia 36 355.36
Since sexual dimorphism is documented for limb bone measurements
(Trinkaus, 1981; Ruff et al., 2002), an examination of differences based on sex
within and between groups is warranted. As would be expected, males in each
population exhibited longer mean values than females for all limb bones (see Table
5.6 for mean values). However, the brachial and crural indices did not follow a
consistent pattern. In the Nubian population, males possess mean brachial and crural
indices that are higher than females. For the Alaskan/Aleut group, males also
possess a higher brachial index, but the crural is only slightly higher in males and for
the Thai population, females possess slightly higher values than males for both
brachial and crural indices.
Using a t-test for independent samples of means for males versus females,
some of the variables were found to be different between the sexes (see Table 5.7 for
index results). Within the Nubian population, males and females were found to be
significantly different from each other in brachial indices, but not in crural. However,
component bones were all significantly different for males and females (p<0.001 in
all cases). The same pattern held true for male and female indices from the
Alaskan/Aleutian populations and for the Thai populations. As with the Nubians,
sexual dimorphism was in all individual limb bones (p<0.001 for all but the tibia
among the Thai, where p=0.002).
Table 5.6 Mean measurements by sex and population.
Population Measurement Sex N Mean
Kulubnarti, Nubia Brachial Index Male 26 79.65
Female 22 77.93
Humerus Male 26 321.50
Female 22 293.82
Radius Male 26 256.03
Female 22 228.80
Crural Index Male 26 86.73
Female 22 85.66
Femur Male 26 444.83
Female 22 411.30
Tibia Male 26 385.69
Female 22 352.11
Alaska/Aleutian Brachial Index Male 24 75.18
Islands Female 24 72.49
Humerus Male 24 306.94
Female 24 283.26
Radius Male 24 230.61
Female 24 205.36
Crural Index Male 29 80.28
Female 24 80.44
Femur Male 29 419.51
Female 24 391.97
Tibia Male 29 336.94
Female 24 315.28
Khok Phanom Di, Brachial Index Male 20 81.85
Thailand Female 23 79.26
Humerus Male 20 308.55
Female 23 287.00
Radius Male 20 252.45
Female 23 227.43
Crural Index Male 17 84.12
Female 19 84.91
Femur Male 17 435.18
Female 19 407.11
Tibia Male 17 366.18
Female 19 345.74
Table 5.7 Comparison of mean differences by sex, T-test results
Adult Population Comparison by Sex, p-values
Brachial Index Crural Index
Kulubnarti, Nubia 0.005* 0.101
Alaska/Aleutian Islands <0.001* 0.823
Khok Phanom Di, Thailand 0.002* 0.225
An analysis of variance was used to examine whether there is a significant
difference between populations by sex. For males, all three groups differed
significantly in brachial and crural indices (Tables 5.8 and 5.9). Females from Nubia
and Thailand were not significantly different from each other for the brachial or
crural index (Tables 5.8 and 5.9), although both were significantly different from the
Alaskan/Aleut population. Based on these results, the males seem to be driving the
between-population variation more than the females.
Despite the presence of sexual dimorphism within all three populations for all
limb bones, only the brachial index shows a pattern of dimorphism. This could be
due the mechanical requirements placed on the lower limbs for bipedal locomotion.
These differences cannot be tested in juveniles within the current study as they are
not divided by sex. However, the differences in adults based on sex observed here
may be useful in interpreting juvenile data where those indicators are available.
Table 5.8 Comparison of brachial indices by sex, ANOVA results
Male Adult Population Comparison of Brachial Indices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Nubian Alaskan/Aleut <0.001* Thai 0.014* <0.001*
Overall difference between groups, p-value <0.001*
Female Adult Population Comparison of Brachial Indices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Nubian Alaska/Aleut <0.001* Thai 0.133 <0.001*
Overall difference between groups, p-value <0.001*
Table 5.9 Comparison of crural indices by sex, ANOVA results
Male Adult Population Comparison of Crural Indices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Nubian Alaskan/Aleut <0.001* Thai 0.001* <0.001*
Overall difference between groups, p-value <0.001*
Female Adult Population Comparison of Crural Indices, p-values
Kulubnarti, Nubia Alaska/Aleutian Islands Khok Phanom Di, Thailand Nubian Alaskan/Aleut <0.001* Thai 0.597 <0.001*
Overall difference between groups, p-value <0.001*
- 51 -
To some extent, the juveniles in this study do conform to the adult
characteristics enumerated above. When grouped together, the juvenile samples
follow the same pattern as the adults for the brachial index the Thai have the
highest mean value (82.16), the Alaskan/Aleuts have the lowest (73.51) and the
Nubian sample is intermediate (78.12). However, unlike the adults for the crural
index, the juvenile Thai sample exhibits the highest mean value (87.25) and Nubians
are intermediate (84.93), though the Alaskan/Aleuts are still the lowest (79.86).
Results are displayed in Figure 5.3. This is a different pattern than seen in the adult
reference samples, where the Nubians possess the highest crural index (Figure 5.2).
As with the adults, all juvenile groups are statistically different from one another for
both indices (Table 5.10).
Juvenile Mean Values
Kulubnarti, Nubia Alaska/Aleutian Khok Phanom Di,
Figure 5.3 Mean Values for Juvenile Indices.
Table 5.10 Comparison of juvenile mean indices, ANOVA results
Juvenile Population Comparison of Brachial Indices, p-values
Nubian Alaskan/Aleut Kulubnarti, Nubia 0.001* Alaska/Aleutian Islands Khok Phanom Di, Thailand Overall difference between groups, p-value <0.001* Thai 0.001* <0.001*
Juvenile Population Comparison of Crural Indices, p-values
Nubian Alaskan/Aleut Kulubnarti, Nubia <0.001* Alaska/Aleutian Islands Khok Phanom Di, Thailand Overall difference between groups, p-value <0.001* Thai <0.001* <0.001*
To elucidate the pattern seen when the juveniles within each population are
compared as a whole to the other populations, a comparison of the age groups
specified in the previous chapter is needed. Mean values for indices and component
bones are listed in Table 5.11 by age group and population. An analysis of variance
was carried out on the three populations by age group (Table 5.12), though several of
the age categories did not possess enough data to be statistically analyzed. A
minimum of 2 measurements was required in each category to perform post-hoc tests
for significance. Figures 5.4 and 5.5 provide a visual reference for the patterns of
indices through development, especially useful for interpreting those age groups that
have small samples.
For Age Group 1 (fetal Oy), the populations are all characterized by higher
indices than the adult reference sample and are all very similar in value, though the
Alaska/Aleutian Island index means consist of a single individual each. No test for
significance could be completed between all three groups, due to the small Arctic
sample. That the warm-climate Nubian and Thai samples are higher in value than
the adult means is remarkable. However, the Alaskan/Aleut sample is the real
anomaly, exhibiting tropical index values. While these may be due to the single
measurement, the results for the next age group continue this pattern.
Table 5.10 Mean values of measurements for juveniles by population and age category.
Population Measurement Age Group 1 Fetal 0y Age Group 2 0.1 1.5y Age Group 3 1.6 2.5y Age Group 4 2.6 4.5y Age Group 5 4.6 6.5y Age Group 6 6.6 8.5y Age Group 7 8.6- 10.5y Age Group 8 10.6- 11.5y
Kulubnarti, Nubia Brachial 81.18 78.68 76.35 77.35 77.38 77.99 78.57 79.12
Crural Index 88.32 84.24 83.33 84.97 85.45 85.67 84.34 84.93
Humerus 66.4 91.7 115.8 129.0 148.4 176.0 181.9 211.9
Radius 54.1 71.8 88.1 99.2 115.0 134.8 142.5 165.3
Femur 79.3 115.7 148.8 173.2 205.2 249.8 260.4 294.7
Tibia 64.0 99.4 123.4 145.8 177.5 211.6 218.3 248.5
Alaska/ Brachial 80.26 80.41 71.51 71.82 72.09 71.22 73.15 73.93
Aleutian Islands Crural Index 87.53 81.74 79.38 79.80 78.43 79.77 78.18 78.37
Humerus 59.6 87.8 116.4 132.6 145.8 185.1 197.8 217.7
Radius 46.1 71.4 84.3 93.1 105.6 130.2 149.5 159.8
Femur 64.8 112.9 148.8 171.3 195.0 234.9 276.1 316.4
Tibia 61.7 94.2 123.9 134.6 151.1 192.5 207.3 250.6
Khok Phanom Di, Brachial 82.58 82.45 77.25 85.65 80.91 79.16 80.32
Thailand Crural Index 87.67 85.96 87.22 86.70 84.83
Humerus 63.1 90.5 116.5 129.0 151.0 189.7 205.0 207.0
Radius 52.3 75.5 90.0 117.0 154.0 168.7 165.0
Femur 73.8 107.7 139.3 174.0 209.0 268.0 294.5 295.5
Tibia 63.7 91.9 121.3 149.0 179.0 232.3 220.0 259.7
For Age Group 2 (0.1 1.5y) the Alaskan group mean, now consisting of a
larger sample size (n=7), remains high for the brachial index. The Thai group also
remains higher than the adults reference group, but the Nubian value drops slightly
below the Alaska/Aleut group. There are significant differences between the Thai
and Nubians for brachial indices at this age group, but neither is different from the
intermediate Alaskan/Aleut group. For the crural index, all groups drop in mean
value, though only the Nubians fall below the adult reference values. Statistically,
the intermediate Nubians are not different from the Thai, but are significantly
different from the Alaska/Aleut group. The Thai and Alaska/Aleut groups are also
statistically different from one another.
For Age Groups 3 (1.6 2.5y), 4 (2.6 4.5y), and 5 (4.6 6.5y) the Thai
sample did not have enough measurements to test a difference in means for all
groups. However, there are some observable patterns for the remaining two
populations by looking at the means listed in Table 5.11 and depicted in Figures 5.4
and 5.5. For the brachial index in Age Group 3, both samples drop off appreciably
from the infancy measurements to values slightly below the adult reference sample.
Both remain at these low values through Age Groups 4 and 5, increasing slightly but
not exceeding the adults. Although represented by a single measurement, the Thai
sample for Age Group 3 also drops below the adult values.
For crural indices, as with the brachial, the Alaskan/Aleut and Nubian
groups drop in mean values from the earlier age groups. However, this drop off is
less dramatic and for the Thai population the mean value actually increases at Age
Group 3 to exceed that of Age Group 1. However, the Thai value for Age Groups 3
and 5 are single measures and may not be representative.
For Age Group 6 (6.6 8.5y), the Alaskan/Aleut population is significantly
different from both the Thai and Nubian groups for brachial and crural indices.
However, the Nubian and Thai samples are not statistically different from one
another. This is a more expected pattern, with the warm-climate populations being
different from the cold-climate Alaskan/Aleut sample. An examination of the mean
values themselves reveals that all three populations are starting to appear like the
adult reference samples with a few notes. All means for the Nubian and
Alaska/Aleutian Islands groups are slightly below adult values, while the Thai
sample remains slightly above for the brachial index and very high for the crural
Age Group 7 (8.6 10.5y) was also unable to be tested for significant
differences do to the small Thai sample size. However, an examination of the
descriptive statistics show that all population means are similar to adult brachial
means. The Thai sample mean does fall below the adults, but as it is based on a
single measurement this may be random. For the crural index, the Nubian and
Alaskan/Aleut groups are below the adult means, while the Thai sample has no data.
For Age Group 8 (10.6 11,5y), the brachial indices and crural indices are different
between the Alaskan/Aleut sample and the others, while the Thai and Nubian
samples are not statistically different from one another as with Age Group 6.
The most apparent trend across these age groups is the high index values for
all groups at the earliest ages. There is a marked difference in brachial index values
for juveniles from birth to approximately 1 Vi years of age. In all groups these values
are well above adult indices. The pattern in the lower limb segments is less
pronounced, but all values are high for at least the first age group, after which there
is a drop off for all groups.
- 58 -
Khok Phanom Di, Thailand
Figure 5.4 Brachial Indices By Age Group For Study Populations. (Note that last
age group 9 represents adult reference sample.)
Khok Phanom Di, Thailand
Figure 5.5 Crural Indices By Age Group For Study Populations. (Note that last age
group 9 represents adult reference sample.)
Table 5.12 Comparison of juvenile indices by age group, ANOVA results.
Juvenile Brachial Index Comparison p-values
Nubian Alaskan/Aleut Thai
Age Group 1 (Fetal/Perinatal) NA NA
Age Group 2 (0.1 -1.5 years) 0.314 0.002*
Age Group 3 (1.6-2.5 years) NA NA
Age Group 4 (2.6-4.5 years) NA NA
Age Group 5 (4.6-6.5 years) NA NA
Age Group 6 (6.6-8.5 years) 0.001* 0.389
Age Group 7 (8.6-10.5 years) NA NA
Age Group 8 (10.6-12.5 years) 0.041* 0.895
Age Group 1 (Fetal/Perinatal) NA
Age Group 2 (0.1-1.5 years) 0.253
Age Group 3 (1.6-2.5 years) 0.113
Age Group 4 (2.6-4.5 years) NA
Age Group 5 (4.6-6.5 years) NA
Age Group 6 (6.6-8.5 years) 0.003*
Age Group 7 (8.6-10.5 years) NA
Age Group 8 (10.6-12.5 years) 0.007*
Juvenile Crural Index Comparison p-values
Nubian Alaskan/Aleut Thai
Age Group 1 (Fetal/Perinatal) NA NA
Age Group 2 (0.1-1.5 years) 0.048* 0.307
Age Group 3 (1.6-2.5 years) 0.542 0.305
Age Group 4 (2.6-4.5 years) NA NA
Age Group 5 (4.6-6.5 years) NA NA
Age Group 6 (6.6-8.5 years) 0.004* 0.736
Age Group 7 (8.6-10.5 years) NA NA
Age Group 8 (10.6-12.5 years) 0.001* 0.997
Age Group 1 (Fetal/Perinatal) NA
Age Group 2 (0.1 -1.5 years) 0.009*
Age Group 3 (1.6-2.5 years) 0.072
Age Group 4 (2.6-4.5 years) NA
Age Group 5 (4.6-6.5 years) NA
Age Group 6 (6.6-8.5 years) 0.007*
Age Group 7 (8.6-10.5 years) NA
Age Group 8 (10.6-12.5 years) 0.003*
Since previous research indicates that nutritional differences existed between
the two subpopulations from Kulubnarti, Nubia, a t-test for independent samples was
computed to determine if the two subgroups from different cemeteries were
significantly different from each other. As with adults, no significance was found
between the two cemeteries for brachial indices (p = 0.389) or crural indices (p =
249). When compared to the other juvenile populations, the two sub-populations of
the Nubian group are still not significantly different from each other (p = 0.964 for
brachial index and p = 0.939 for crural index). In almost every case, the nutritionally
stressed earlier cemetery sample actually had longer means measurements for each
limb segment across all age groups. While nutritional differences undoubtedly had
an effect on the limb bones of these subgroups (Albert and Green, 1999), it does not
seem to be relevant in the current analyses.
Since only mean data were available for limb bones from publish studies,
brachial and crural indices calculated for these groups are not directly comparable to
the three populations with individual measurements (Ruff et al., 2002). Statistical
analyses were not performed on the data from these groups, but they are included for
discussion purposes as patterns may still be observed.
Mean values for brachial and crural indices of the three primary populations
were compared to mean values calculated from the means of each component bone.
This resulted in the same pattern, if not the exact same values, indicating that
brachial and crural indices calculated from mean values for long bones are still
loosely comparable to mean values of indices derived from individual measurements.
Mean values for brachial and crural indices from the three study populations and
those calculated from the published data were plotted against age and shown in
figures 5.6 and 5.7. Since there were variations in the age categories used by other
authors, the midpoint of each category was used for graphing. These graphs
demonstrate a pattern that is similar to the results for the three groups with individual
data (Figures 5.4 and 5.5). All of the populations cluster together for the earliest age
groups, indicating that the trend seen in the earlier analysis is present in other groups
To add further clarity to the results of Figures 5.6 and 5.7, a regression of
mean index values was performed on latitude including all juvenile populations
(Figures 5.8 and 5.9). Latitudes were available for each site in the study (listed in
Chapter 4) except for the Alaskan/Aleutian Island group, which was widely
dispersed across the state of Alaska. For this group, the latitude for the geographical
center of the state was used. Figures 5.8 and 5.9 include a trend line for the
regression. All latitudes are north of the equator except that for K2, South Africa,
which is obviously south, but for comparison, all latitudes are plotted as absolute
distance from the equator. Even with the variation within populations across age
groups (displayed in Figures 5.6 and 5.7), there is a clear pattern between index
values and latitude. This is consistent with previous research using adult populations
from ecogeographically disparate populations (Schultz, 1937; Roberts, 1978;
Trinkaus, 1981; Ruff, 1994; Holliday and Ruff, 2001).
A A OO 2 8 o A o $ A &
o Kulubnarti, Nubia
A Khok Phanom Di, Thailand
A Indian Knoll, Kentucky
Arikara, South Dakota
O K2, South Africa
-1 0 1 2 3 4 5 6 7 8 9 10 11 12
Age Range Midpoints (in years)
Figure 5.6 Brachial Indices By Age Group For Study Populations and Additional
85.00 X o ~o V A A 6 O & 4 A O o A
= 80.00 a DdO
o Kulubnarti, Nubia
A Khok Pbanom Di, Thailand
A Indian Knoll, Kentucky
Arikara, South Dakota
O K2, South Africa
-1 0 1 2 3 4 5 6 7. 8 9 10 11 12
Age Range Midpoints (in years)
Figure 5.7 Crural Indices By Age Group For Study Populations and Additional
Figure 5.8 Plot of Mean Indices for Juvenile Populations Versus Latitude.
As expected from the results of previous studies (Trinkaus, 1981; Ruff, 1994;
Ruff et al., 2002), the three populations are different from each other in brachial and
crural indices and generally follow expected patterns of clinal variation with the cold
population of Alaskans/Aleuts exhibiting the smallest indices and the warm climate
populations possessing higher indices. This is especially clear in adults, although,
there are several interesting characteristics for the juvenile populations that do not
strictly conform to this pattern.
The adult populations generally conform to expectations and results from
previous research (Trinkaus, 1981; Ruff, 1994). Populations from different regions
are characterized by different limb proportions with the cold-adapted population
from Alaska and the Aleutian Islands exhibiting shortened limb segments, but
particularly the distal elements. Despite having some individual measurements that
are high compared to the warm-climate populations, the Alaskan/Aleut group are
still characterized by relatively short distal segments. The populations from
Thailand and Sudanese Nubia trade off over which has the highest index for each
appendage, but both are higher than the cold adapted group. Since both are tropical,
this is consistent with previous studies (Trinkaus, 1981; Ruff, 1994), but the
difference in humidity level may have an effect on the pattern seen. Humidity is
believed to create greater selective pressure for a more linear body form (Baker,
1960; James, 1970), so it follows that the specimens from the Khok Phanom Di site
in Thailand would have higher values for indices than those from Kulubnarti, Nubia.
As this is only found to be true in the brachial index and not in the crural index, it is
possible that the pattern found in the Thai is the result of another mechanism. The
possibility that lower limb bones are also under selective pressure from locomotion
(Holliday, 1999) may influence the pattern with the Thai group. Already
characterized as short (Tayles, 1999), the inhabitants of Khok Phanom Di may have
adapted to the warm, humid climate through lengthening of the upper limb (primarily
in the radius) while locomotor energetics may have required the lower limb
proportions to remain more stable.
While the results show that sexual dimorphism is present to some extent
among adults in all populations, the ranking of each population based on indices in
relation to the others is not affected. Therefore, sexual dimorphism should be
considered when comparing populations, but may not have a large effect on the
comparisons between populations from different climates. As mentioned in Chapter
- 66 -
2, research indicates that there is little sexual dimorphism in pre-adolescent limb
segments (Anderson and Greene, 1948; Ruff, 2003; Smith and Buschang, 2004).
In the juvenile samples, the unevenness of limb proportions throughout
growth is clear. Early childhood with its high index values for all groups is distinctly
different from mid- to late childhood, where indices are more consistent with adult
values. This is particularly remarkable for the Alaskan/Aleut sample because of its
similarity to the warm-adapted populations at birth and in early childhood. While the
Alaskan/Aleut sample has only a single measure for the earliest age category
(fetal/newborn), the next age group also demonstrates this pattern, suggesting the
early measurement is not an anomaly. These results are contrary to research that
suggests that newborns possess adult body proportions (Schultz, 1923; Lim et al.,
2000; Warren et al., 2002). The distinct pattern of differences between infancy and
mid- to late childhood might be the result of a shift from crawling to walking, but
research by Ruff (2003) concludes that bone length is not greatly influenced by a
The more probable explanation is the variable rates of growth for individual
limb segments. As discussed in Chapter 2, proximal and distal limb segments
generally grow at variable rates (Ulijaszek et al., 1998; Smith and Buschang, 2004).
Figures 6.1-6.4 demonstrate this pattern in the limb bones of the sample populations.
The patterns exhibited by the radius and tibia differ from that of the humerus
and femur. All populations start at similar values for all four limb bones. However,
while the proximal segments have similar endpoints, the variation among
populations is far more pronounced in the distal segments. This divergence becomes
more distinct by midchildhood, though some of the variation in the Thai group may
be due to the very small sample sizes for the mid- and late childhood age ranges.
The graphs also clearly demonstrate that it is the distal segments that are
primarily responsible for the differences in index values between the
Alaska/Aleutian Islands group and other two populations, except in midchildhood.
For a few middle age groups, the Alaska/Aleutian Islands sample are characterized
by relatively long humeri compared to the Nubian group. However, this still shows a
divergence in relative limb lengths starting in midchildhood. Overall, these results
support the findings by yEdynak (1976) that native Alaskan children exhibit
relatively shortened distal elements by the age of 2 years old. Unfortunately, her
study does not include data on earlier ages, so no comparison can be made here.
Research by Jamison (1976) of living native Alaskans also fits with the current
findings. The results of that study indicate that juveniles in the study did not exhibit
the characteristically shorter stature until after 4 years of age. Taken together, these
results indicate that cold-adapted body proportions develop after early childhood.
Radius (mm) CTO Humerus (mm)
Mean Humeral Values
- c> Kulubnarti, Nubia
t, Khok Phanom Di, Thailand
re 6.1 Mean Humeral Values for Study Populations by Age Group.
Mean Radial Values
- o Kulubnarti, Nubia
a Khok Phanom Di, Thailand
Figure 6.2 Mean Radial Values for Study Populations by Age Group.
Mean Femoral Values
- o Kulubnarti, Nubia
------- Alaska/Aleutian Islands
6 Khok Phanom Di, Thailand
Figure 6.3 Mean Femoral Values for Study Populations by Age Group.
Mean Tibial Values
- o - Kulubnarti, Nubia
Khok Phanom Di, Thailand
Figure 6.4 Mean Tibial Values for Study Populations by Age Group.
Another pattern emerges when the earlier age groups are removed from the
graphs of mean index values (Figures 6.5 and 6.6). Without the high mean values
for the juveniles under the age of 1 'A years of age, the crural index appears to remain
fairly stable throughout development. There are fluctuations, but no distinct pattern
emerges and all values appear fairly close (Figure 6.6). However, the brachial index
seems to increase until adulthood after the initial drop off in value from early
childhood. This is difficult to explain given the pattern observed for the individual
limb segments. In fact, the opposite pattern would seem to be likely based on
findings by Buschang (1982) of limb growth, which found that the humerus
maintained greater allometric growth than the radius. However, his research also
established greater allometry for the tibia than femur. This fits with the results here
suggesting a more stable crural index after early childhood. Though the femur
experiences more absolute growth, the tibia keeps better pace with it than the radius
does with the humerus. While Ruffs research (2003) doesnt support a shift in
locomotion causing a change in lower limb lengths, it may be that the mechanical
constraints of bipedal locomotion generally stabilize limb proportions.
Of course, some of the irregularity observed might be a result of the uneven
age distribution between sample populations. While this is undesirable, it is a
common problem with skeletal samples. Here, the Thai population is characterized
by a high number of newborns while the Alaskan/Aleut sample has more specimens
in the middle age range.
- 71 -
3 4 5 6 7 8 9
o Brachial Index
a Brachial Index Khok
Phanom Di, Thailand
Figure 6.5 Brachial Indices by Age Group with Trendlines.
o Crural Index
a Crural Index Khok
Phanom Di, Thailand
3 4 5 6 7 8 9
Figure 6.6 Crural Indices by Age Group with Trendlines.
When nutritional differences within the Nubian sample were considered as a
possible confounding factor, it was found to be non-significant in the present study
for both adults and juveniles. Although certainly differences do exist for the Nubian
population and have been previously documented (Albert and Greene, 1999), they do
not seem to have any influence on comparisons to other populations when examining
brachial and crural indices. This coincides with findings by Katzmarzyk and
Leonard (1998) that body proportions are less likely to be influenced by external
When looking at the pattern between the Nubian groups, it is striking that the
more nutritionally stressed early cemetery exhibits higher values than the later
cemetery for bones and indices in almost every case. This decrease in size suggests
that any differences in proportions between the groups are likely to be the result of
shifts in the gene pool of the population (Moore et al., 1986). It is probable that any
nutritional improvements over time from the early to later group would result in an
increase in bone lengths rather than the decrease seen here. The conclusion then is
that the effects of nutrition are limited for the variables examined in this study and
are unlikely to impact the use of brachial and crural indices as phylogenetic markers
for climatically disparate populations.
- 73 -
Comparison to Published Data and Research
Like the results for age groups in the three primary populations, the indices
derived from published data for other populations do not remain constant throughout
development (see Figures 5.6 and 5.7). As with the Nubian, Alaskan/Aleut, and Thai
populations, the additional groups generally cluster together for the earliest ages.
This is in keeping with the studies of Johnston (1962) and Merchant and Ubelaker
(1977) which find that at very early ages the Indian Knoll and Arikara, respectively,
are similar to each other and to a Euro American reference sample in growth of the
limb bones. This suggests that juveniles are similar during infancy and early
development with little influence from population affinity. After early childhood, the
two populations diverge from the reference sample but remain similar to each other
(Merchant and Ubelaker, 1977). This indicates that the two Native American
populations, which are separated both temporally and culturally (Merchant and
Ubelaker, 1977), are still more similar to each other than to Caucasian groups.
Variation appears to be more pronounced in the brachial index than crural.
As discussed above, this may be due the constraints of bipedalism. Sundick (1978)
reported corresponding results in his study comparing the populations from
Altenerding and Indian Knoll. These two climatically and genetically disparate
groups exhibited far less variation in lower limb segments from each other than in
the upper limb.
Excluding the earliest age groups, the results are generally consistent with
expectation for ecogeographical patterning. The juveniles from the tropical K2 site
in South Africa have the highest brachial index at almost every age value and the
Alaskan/Aleut sample remains the lowest except at birth. The indices for the
populations from colder Altenerding, Germany are lower than all but the
Alaskan/Aleut sample for most ages. The Native American samples from Indian
Knoll and the Arikara, being from temperate regions should fall near the middle.
This is by and large the case, though there are a few fluctuations.
A few anomalous trends bear closer examination. For crural indices, the
Arikara are occasionally higher within an age range and the K2 sample falls more
toward the middle below the Thai and Nubian samples. This is not expected, since
the K2 populations represents a tropical latitude and it follows that this population
would possess values among the highest. Steyn and Henneberg (1996) indicate that
the K2 inhabitants were unlikely to have been under nutritional stress. However, the
lower limbs are more likely to be affected by any decrease in nutritional levels
(Steyn and Henneberg, 1996). In almost all case for the K2 population and in the
older age groups for the Arikara, the sample sizes are very small and occasionally
only a single individual.
Examining the cold climate population from Altenerding shows that it often
falls below even the Alaskan/Aleut sample for several ages. Again, this is
unexpected as the Alaskan/Aleut group inhabits the highest latitude and should
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possess the lowest values. As for the previous examples, the small sample size for
many of the variables may contribute to the anomalies seen here.
The regression of index value against latitude (Figure 5.8) demonstrates fairly
strong evidence for ecogeographical patterning despite the variance discussed above.
Even including the anomalous early childhood ages to calculate a single juvenile
index for each population results in a consistent model (R2 = 0.7805 for brachial
index, R = 0.8346 for crural index). Despite any differences in proportions
between early childhood and later ages, the broad relationship among populations
corresponds to climatic differences.
While others have asserted that limb proportions are the result of genetic
adaptation (Lim et al., 2000; Warren et al., 2002), the findings here suggest that
developmental processes during early childhood, particularly in the case of the cold-
adapted Aleuts and native Alaskans, may be as important in achieving those
proportions. This does not negate a genetic explanation for variation in body
proportions. However, the results do demonstrate that a more complex process is at
work. A larger scale study including more individuals would be required to ensure
that the results here are not the result of unequally distributed sample, though that
will be difficult to achieve using archaeological populations. Although some
measures of body proportions have been examined in juveniles from immigrant
populations, these use the sitting height/height ratio (Eveleth and Tanner, 1976;
Cheng et al., 1996; Bogin and Rios, 2003). Examining brachial and crural indices in
children immigrating to markedly different climates would provide a test of the
results presented here. Shifts in limb proportions from generation to generation of
immigrants would indicate that direct exposure to an environment is integral in
creating the distinctive body forms seen in different populations.
The results here also have implications for studies in paleoanthropology as
well as modem human variation. Brachial and crural index differences have been
well established as defining characteristics for recent hominid groups (Trinkaus,
1981; Ruff, 1994; Holliday, 1999). A recent assessment of the Abrigo do Lagar
Velho juvenile by Ruff, et al. (2002) included a comparison of brachial and crural
indices to assist in assigning the skeleton to a hominid group. While the authors
draw very tentative conclusions, their assessment is based on comparisons to more
recent groups from eco-geographically disparate populations and the assumption that
adults and juveniles from the same group possess similar index values. In their study
the age examined is limited to a small range (4-6 years old) and in this case,
consistent patterns between adults and juveniles are present. The results of the
present study indicate that by this age, populational differences are apparent.
However, conclusions drawn from data for fetal and early childhood specimens
should be treated cautiously, since evidence here suggests that brachial and crural
indices may not reach adult values until later in development. Undoubtedly, the use
of means to calculate indices and the inconsistent and often small sample sizes has
influenced patterns observed. However, the results of this study suggest that while
clinal variation does exist in juveniles, the use of brachial and crural indices as
phylogenetic markers may provide inaccurate results at very young ages.
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