Keywords: morphology, adaptation, climate, Russians, Buryats
The ecological and climatic peculiarities
of an area where an anthropological group was formed influence human morphophysiological
characteristics. The influence of extremely strong climatic factors
may lead to genetic adaptation and evolutionary changes in a gene pool
from generation to generation, thereby enhancing the biological success
of a population (Wolanski, N., 1990). This process results in the formation
of highly adapted groups,
However, morphofunctional adaptation to particular geographical conditions can be traced in a population not at once, but long after the population's arrival in the new ecological environment. In some cases an organism's "conservatism" can lead to incomplete adaptation for several generations. One example of this situation is the old-resident population of Eastern Siberian (Trans-Baikal) Russians, living in the territory of the Buryat Republic.
The Buryat Republic is located in the Trans-Baikal region of Eastern Siberia, in a zone of severe continental climate with an annual temperature fluctuation of more than 48 degrees. It is assumed that these climatic extremities exert an influence on the human organism. The Buryats are the indigenous population in the Trans-Baikal region; their peculiar morphological complex was formed in the Bronze Age in this region, where the modern Buryats reside (Alexeev, V., Gochman, I., 1983). The number of Buryats in the Russian Federation is 385 thousand. On the other hand, as many as 648 thousand Russians live in the same territory. The first immigration of the Russian population into Buryatia goes back to the 17th century. Thus, the modern Trans-Baikal Russian residents are the result of Russian and Buryat mixing which took place over eight or nine generations. The serological index of the mixture in the Russians of Buryatia is about 40% (Bounak, V., 1963).
The subjects of this research were representatives of indigenous and old Russian residents of Eastern and Western Siberia. Anthropometric examination was undertaken on young adults (304 males and 391 females between ages 18 and 25) free of any genetic or chronic diseases; they were all students of Tjumen (Western Siberia) University and Ulan-Ude (Buryat Republic, Eastern Siberia) University. The subjects' parents and grandparents had been born and lived in the same regions where the examination was undertaken, and no subject's pedigree included interethnic marriage for at least two prior generations.
According to the climatic and geographical conditions these subjects are subdivided into two ecotypological groups (ecotypes), i.e., a temperate climate group (the Russians of Western Siberia) and severe continental climate groups (the Buryats and the Russians of the Buryat Republic, Eastern Siberia).
Anthropometric dimensions were measured
by a single observer (AK), including stature, weight, circumferences (upper
arm, forearm, thigh and calf), diameters (elbow, wrist, knee and ankle),
and skinfold thicknesses (eight in the males and seven in the females).
All subjects were measured in light clothing without shoes following standard
methods outlined in Lothman
Weight was determined to within
In a study of the body constitution
the Body Mass Index (BMI, or Quetelet-Kaup-Gould, or
The body build components of each
subject were calculated using Matiegka's (1921) formulas. Namely, the amount
of muscular tissue
M = L × r2 × 6.5 ,
where L is the stature (cm), and r is the mean average of upper arm, forearm, thigh and calf radiuses (excluding the thickness of subcutaneous fat and skin) (cm).
The amount of fat tissue (D, kg)
was calculated according to the formula:
D = 0.5 × d × S × 0.13 ,
where d is the average skinfold thickness
(mm), and S is the body surface area (sq.m), the latter calculated according
to the formula:
S = W0.425 × L0.175× 74.66 ,
where W is weight (kg), and L is stature (cm).
Body build components in each subject were compared in relative figures (percentage to weight).
Topography of subcutaneous fat was estimated from four skinfold thicknesses: subscapular, triceps, suprailiac and calf. The amount above the waist (AW) was defined as the sum of subscapular and triceps skinfolds; that below the waist (BW) as the sum of suprailiac and calf skinfolds; that of the trunk (TR) as subscapular and suprailiac skinfolds; and that of the extremities (EXT) as triceps and calf skinfolds. The largest among these four sums in a given subject determines the type of this subject's subcutaneous fat topography. The percentage of subjects in each type of fat topography was obtained in each group.
In order to evaluate body proportions, we classified the relative shoulder breadth to stature of each subject into the three groups:
In tables 1 and 2, the mean and SD of six measurements, two indices, and relative muscular and fat tissue components to weight are presented for males and females independently.
The two groups of Siberian Russians of either sex were taller and heavier than the Buryats (P<0.05 in all cases, except the weight between Western Siberian Russian women and Buryat women).
As for relative shoulder breadth to stature, the distribution among the Western and Eastern Siberian Russians is close to normal distribution, i.e., to the Gaussian curve, where 50% of the subjects correspond to the second group (Mean ± 0.67·SD, mesomorph group) and the remainder belong to the first and third groups (the dolichomorph and brachimorph groups each with 25%). Thus the frequency of dolicho-, meso- and brachimorphs among the Russians of Eastern and Western Siberia is approximately 25%, 50%, and 25% respectively.
However, of the Buryat males and
females up to 70% are characterized mesomorphs, and about 30% of the Buryats
belong to marginal groupings,
The amount of muscular tissue M varies
only slightly among the three investigated groups. In contrast, the
differences in the amount of fat tissue D are more substantial. Although
the results of skinfold thickness studies have been widely published (Leonard, W.
The topography of subcutaneous fat
is an important characteristic in these different groups (Figures 1, 2).
In the males, subcutaneous fat is mostly located below the waist; more
precisely, adipose tissue in Western Siberian Russian men is mostly located
on the lower trunk (the suprailiac), while in Buryat men it is located
on the lower limbs (the calf), and in Eastern Siberian Russian men almost
equally on the lower trunk and limbs. In the Western and Eastern Siberian
Russian females, subcutaneous fat tissue is mostly concentrated on the
trunk below the waist and the lower limbs. In contrast, the Buryat women
are characterized by a greater amount of fat tissue on the trunk.
Figure 1 Percentage of subjects displaying each type of subcutaneous fat topography (Males).
Figure 2 Percentage of subjects displaying each type of subcutaneous fat topography (Females).
The Analysis of Variance (ANOVA) shows that the Rohrer index of both the males and females is significantly influenced by the ecotype (Table 3). In the males, both the muscular and fat components are similar in the different climatic groups (Table 1, 3). In the females, however, the muscular and fat components confirm the influence of the ecotype factor (P<0.05), according to the ANOVA; that is to say, the ecotypological groups in the severe continental climate (the Buryat and Eastern Siberian Russian women) and in the temperate climate (the Western Siberian Russian women) are opposed to each other.
On the other hand, the body proportions do not manifest any relationships between the climatic and geographical conditions in either sex. The weight-stature indices (the Rohrer index and the BMI) and the relative muscular and fat components are variable, since they vary in accordance with social conditions, nutritional differences and so on.
As Purunjan and Deriabin (1979) indicated, stature, body proportions and the topography of subcutaneous fat tissue are more stable, because they are regulated by the endocrine system, which is less susceptible to change under the influence of climatic factors. In our subjects, stature and body proportions were stable in either sex, but as for relative muscular and fat components to weight these were stable only in the males whereas for subcutaneous fat topography these was so only in the females.
As for ethnic membership factors
The peculiar topography of subcutaneous
fat tissue can be traced in the males' ecotypological groups (Fig. 1) vs.
The Eastern Siberian Russians preserved the main traits which characterize the original type of temperate climatic zone population.
The stressful influence of the East Siberian continental climate led to morphological changes in the Russian inhabitants of the region. However, morphological adaptation to this climatic influence was more complete in the Russian males than females. In respect of such important ecotypological characteristics as weight-stature interrelationships and subcutaneous fat topography the Eastern Siberian Russian males were closer to the indigenous population of the severe continental climatic zone (the Buryats) than to the Russians of the temperate climatic zone.
In the same respect (stature, proportions, subcutaneous fat distribution) the Russian Eastern Siberian females were closer to representatives of their own ethnic group still living in the temperate climate conditions. This is evidence of their being less adapted to the climatic conditions.
We assume that in this case the "conservatism" of the female gene pool can lead to chronic stress caused by incomplete adaptation to the influence of a severe continental climate.
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|Last updated 08.12.04
© A.Kozlov, G.Vershubsky