Index Introduction Subjects and Methods Results Discussion Physical status of the present-day adult Javanese Secular change in Javanese and in Japanese References

Introduction

The body size and shape of humans reflect the socioeconomic, especially nutritional, status in which the subjects live, as well as the vestigial evolutionary adaptations to natural conditions. In general, in the same or in closely related species of warm-blooded animals, two rules of zoogeographical variation of size and shape from the viewpoint of thermoregulation are recognized, i.e. Allen’s rule (1877) and Bergmann’s rule (1847, cited in Roberts, 1953; Newman, 1953; Schreider, 1971; Crognier, 1981). Both indicate that a smaller body surface area relative to body volume gives off less body heat. Allen (1877) attributed thermoregulation to variation of long/short protuberances of the body, e.g. the ear or the extremities, whereas Bergmann attributed it to the size/weight of the body.

In contrast to the richness of paleoanthropological remains and studies since the excavation of Homo erectus in Java and successive findings in that country, few studies on living humans in Indonesia have been carried out. The study of living humans is important in order to reconstruct human evolution. It is necessary to distinguish genetically fixed physical characteristics from variable characteristics which take place in the course of evolution (Ruff, 2005). After leaving Africa between 100000 and 50000 years ago, the Mongoloid group went north then east, and arrived in Beringia by 15000–35000 years ago (Cavalli-Sforza, 2000). One group of Mongoloids diverged somewhere in the Middle East, making their way southward as far as Australia via the Malay peninsula, and the other group continued the dispersal eastward to Siberia, Alaska and eventually to South America. The time of bifurcation is uncertain: geneticists, paleoanthropologists, and linguists have proposed greatly differing dates based on their particular disciplines.

Southern and northern Mongoloid groups are each considered to have physically adapted to their respective habitats. It is certain that the modern Javanese and Japanese are good representatives of the southern and northern groups of Mongoloids, respectively. Only one growth and somatotype study on children (Rahmawati et al., 2004) and another on the body size of adults measured in 1944–1945 (Tukuda, 1959) in Indonesia are available, to our knowledge. Although Tukuda (1959) mentioned that D.J.H. Nyessen had reported adult somatometric data from a very limited locality in Java, he regrettably failed to indicate the source. Other than Indonesian, there are no studies on the southern group, excepting that by Murray (2002). Without indicating the year of examination, he reported somatometric data of Filipino (males only), who are classified in the Neo-Malayan group, the same as Indonesians.

Physical characteristics are known to be epigenetically influenced by environmental factors, such as habitat (urban vs. rural), socioeconomic status, lifestyle, or nutrition. In order to discuss local evolution of human populations, it is essential to control for environmental influence. Body size and body proportions are influenced by prevailing nutritional conditions (Eveleth and Tanner, 1990), and this is also true for Javanese children (Rahmawati et al., 2004): the urban subjects were observed to be taller and heavier than the rural subjects of either sex. Huntsman et al. (2005) noted the trend toward increasing fatness in adult females in Bali associated with a rapid transition from their traditional lifestyle to a “Western” lifestyle. Turning our attention from Indonesia to other parts of the world, several studies on body size and proportions of adults with reference to ecological and/or socioeconomic conditions and to secular change have been carried out (Newman, 1953; Roberts, 1953; Schreider, 1971; Hiernaux et al., 1975; Crognier, 1981; Gupta and Basu, 1981; Froment and Hiernaux, 1984; McCullough, 1982; Shatrugna and Visweswara Rao, 1987; Houghton, 1990; Ashizawa et al., 1994; Katzmarzyk and Leonard, 1998; Ulijaszek, 2001; Murray, 2002; Ashizawa, 2002; Huntsman et al., 2005; Steegmann and Platner, 2005). The trends are positive (increase: e.g. Ulijaszek, 2001), unchanged (McCullough, 1982), or negative (decrease: Shatrugna and Visweswara Rao, 1987) depending on the local environmental conditions and era. Ashizawa (2002) illustrated a decreased leg-length-to-height ratio in Japanese males accompanied by increased weight in the latter half of the 20th century.

As mentioned above, evidence supports two main branches in the dispersion of Mongoloids: one southern and one northern. Present-day Javanese and present-day Japanese can be considered as descendants from the time of bifurcation of the former and of the latter, respectively. In the present study, we measured Javanese in 2005 and compared their body size and proportions with those of present-day Japanese (Research Institute of Human Engineering for Quality of Life, 1997) in order to see if there was an actual difference between these two Mongoloid populations. Moreover, based on somatometric data of adult Javanese and Japanese measured about 60 years ago, in 1944–1945 (Tukuda, 1959; Nishi, 1952), we compared the secular changes of size and proportions between the two populations to examine the specific physical characteristics of southern and northern Mongoloid groups.

Subjects and Methods

The Javanese are the major ethnic group living in Java, Indonesia, and are considered to be the descendants of the southern branch of the Mongoloid group. The subjects were 61 males and 77 females living in Yogyakarta, in their 20s–50s, all investigated in 2005. Among the male subjects, 55% were laborers, 18% were employees, and 7% were farmers; among the female subjects, 40% were laborers, 29% were housewives, and 17% were merchants.

Height, weight, and sitting height were measured using an anthropometer (GPM, Swiss made, 1 mm accuracy) and a digital weighing scale (0.1 kg accuracy). Based on these measurements, body mass index (BMI), leg length (subtracting sitting height from height), and leg-length-to-height ratio were obtained.

The body size and proportions of Javanese subjects were statistically compared with those of present-day adult Japanese measured in 1992–1994 (Research Institute of Human Engineering for Quality of Life, 1997) to identify the physical characteristics of the former population. The statistical comparison was executed for the age groups in their 30s–40s only because of the relatively small number of Javanese subjects in their 20s–50s.

The secular change in size and proportion was determined by comparing these present-day Javanese data with the data obtained by Tukuda in 1944–1945 (Tukuda, 1959) in various localities in Java, from manual laborers in both sexes identified as Javanese. In both groups from Java, the 1944–1945 group and the 2005 group, almost none of the aged subjects could remember the correct date of their birth, so we have had no option other than to trust their declaration of age. The present-day Japanese subjects measured in 1992–1994 (Research Institute of Human Engineering for Quality of Life, 1997) were from all over Japan with a sample number ranging from 972 to 4611 in each age group, and identified by decade as those in their 20s, 30s, 40s, and 50s, respectively. In order to make a comparison with the present-day Japanese, we used somatometric data of Japanese (males only), which Nishi (1952) obtained also in 1944–1945, the same period of the old Javanese group.

Outliers that were greater or smaller than the mean value by 3 standard deviations (SD) in each sex/age group were excluded from further analysis. For this new data set the mean and SD were obtained for comparison. The test of normality (Shapiro–Wilk test) showed that the distributions of all measurements of the groups were normal, except for the weight and leg length in females in their 30s. Therefore we applied the t-test to examine the significance of the difference between the means of the Javanese and the Japanese, assuming normal distributions when the sample number was great enough (>50). For the calculated values (ratios and BMI) of the present-day Japanese group, no statistical test to examine the differences with Javanese values was carried out because the former group values were not obtained for each subject. Their ratios and BMI were calculated from the mean values of the respective measurements.

A statistical comparison of the data sets of the present-day Javanese and the Javanese of 1944–1945 (Tukuda, 1959) could not be executed because of the lack of SD values in the latter, and also because Tukuda combined the subjects aged in their 20s–50s into one group. The secular change in body size in the Javanese, which was obtained by the subtraction of the combined data of the 1944–1945 subjects from those of our present-day subjects, was compared with the change in the Japanese.

Results

The statistical values of the measurements (height, weight, and sitting height) and calculated items (BMI, leg length, and leg-length-to-height ratio) of the males and females are given in Table 1.

Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, and Figure 6 present the size and proportions of the subject Javanese compared with present-day Japanese in each age group. The heavy straight horizontal line superimposed on each figure indicates the mean value of the referred compatriot group of Javanese laborers investigated in 1944–1945 (Tukuda, 1959). Although the ages of the subjects in Tukuda ranged from 20 to 60 years, the author bundled up these into a single adult group. A broken line superimposed on the bar-graph of the Japanese in each age group of males indicates the mean values of the Japanese obtained in 1944–1945 by Nishi (1952).

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Figure 1. Comparison of height between Javanese and Japanese. ***P < 0.001.

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Figure 2. Comparison of weight between Javanese and Japanese. ***P < 0.001.

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Figure 3. Comparison of BMI between Javanese and Japanese.

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Figure 4. Comparison of sitting height between Javanese and Japanese. ***P < 0.001.

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Figure 5. Comparison of leg length between Javanese and Japanese.

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Figure 6. Comparison of leg-length-to-height ratio between Javanese and Japanese.

Discussion

By studying the physical status of the Javanese and Japanese of present-day and of 60 years ago, we can distinguish the physical characteristics of Javanese, and compare the secular change observed in both populations.

Physical status of the present-day adult Javanese

The height and sitting height of the present-day Javanese are shorter than those of the present-day Japanese of both sexes (Figure 1 and Figure 4). The male Javanese are much lighter than the male Japanese, while their female counterparts are as heavy as or even heavier than the Japanese females (Figure 2). This results in a lower BMI in the males and, in contrast, a higher BMI in the females in Java (Figure 3). Leg length in the Javanese is not significantly shorter than that in the Japanese in both sexes (Figure 5). As a consequence, the present-day Javanese show relatively greater leg length to height (Figure 6) in contrast to their Japanese contemporaries.

These differences in body size and shapes between the Javanese and Japanese brings to mind Bergmann’s rule (1847) and Allen’s rule (1877) in zoogeography, which explains body size and shape variation from the viewpoint of thermoregulation (relative surface vs. volume). The geographic gradient (cline) of body size and shape, Bergmann’s and Allen’s rule, was widely reported for human populations as well. Although Roberts (1953) found no clear gradation in South and North America, he did find a clear gradation in Asia and Africa. He suggested that a relationship existed between body weight and mean atmospheric temperature. Newman (1953) found a concentration of shorter people in the lower latitudes of both sides of the equator in South and North American indigenous peoples. Schreider (1971) noticed that, in the hotter climate regions of Africa, the body weight to body surface ratio decreased and the leg length to body weight ratio increased. Ashizawa et al. (1994) compared adult Japanese and West Africans in Mali, a country adjacent to the Sahara and characterized by a hot and extremely dry climate, and found that both leg length and relative leg-length to height in the latter were remarkably greater than in the former, although no statistically significant difference was confirmed for height between these two groups.

The greater leg-length-to-height ratio in the Javanese suggests that the southern Mongoloids have preserved the body shape of modern humans, and that the northern Mongoloids have acquired a specific body shape as a result of adaptation to a cold climate in the course of their expansion toward the north and northeast.

In contrast to absolute and relative leg length, weight and BMI respond very sensitively to socioeconomic status and to self-regulation of caloric intake. Therefore, we can indicate that the Japanese males’ greater weight and BMI than those of Javanese males can be ascribed either to their adaptation to the colder climate or to an excess of food intake. The lower BMI in the female Japanese than that of the female Javanese can perhaps be attributed to their regulation of the increase of body weight either consciously or unconsciously. This is an area for future study.

Secular change in Javanese and in Japanese

This is the first study to show the secular change of physical characteristics in Indonesians. We compared the secular change in males between Javanese and Japanese subjects in the same periods, from 1944–1945 to 2005 for the Javanese and to 1992 for the Japanese.

During these 60 years Javanese males became 3.6 cm taller, and 0.7 cm greater in sitting height, 2.9 cm longer in leg length, and 9.5 kg heavier. In consequence, their BMI increased remarkably, by 2.8 (from 18.6 to 21.4). Relative leg length to height also increased by 0.8. Japanese males became taller (by 6–10 cm), heavier (by 14–15 kg), and greater in sitting height (by 2–3 cm) (P < 0.001) throughout the age groups, from those in their 20s to those in their 50s. This resulted in their BMI increasing from 2.7 to 3.5, their leg length from 4.5 to 6.7 cm, and their leg-length-to-height ratio from 0.9 to 1.4. Thus, the increase in these size measures and proportions was greater in the Japanese than in the Javanese except for BMI. This greater positive secular change in Japan can be explained by the dramatic socioeconomic change, especially the improvement in nutrition, in comparison with Indonesian society.

The increase in the leg-length-to-height ratio in the Japanese means that the increase in leg length has been more remarkable than that in height, i.e. the height increase owes much to an increase in leg length that had been repressed during the Second World War due to malnutrition. The same relation between height and leg length was observed also in the secular change of Japanese children from after the War until the 1980s (Tanner et al., 1982). In Japan, however, this trend of leg-length increase seems to have ceased in the 1980s, i.e. the Japanese attained their maximum height and sustained their original proportions as members of northern branch of Mongoloid populations (Ashizawa, 2002).

The greater absolute and relative leg-length in the present-day Javanese compared with the present-day Japanese were indicated above. Exactly the same observation can be said of these two populations of 60 years ago (Figure 5 and Figure 6). Tukuda (1959) also noted that the Chinese and the Japanese in Java at that time had a proportionally great sitting height, meaning relatively short leg length. For that reason we can conclude that the difference in body proportions, such as the leg-length-to-height ratio, between northern (Chinese and Japanese) and southern (Javanese) Mongoloid groups appears to have been conserved from 60 years ago to the present day. This means that the micro/local ecological changes for decades or a century and more have not led to any drastic reform to human body shape.

The greater leg-length-to-height ratio in the Javanese, observed both in the present-day subjects and those of 60 years ago in comparison with their Japanese contemporaries must be a general characteristic of the descendants of the southern branch of Mongoloids (Proto-Mongoloids?). By contrast, the lower leg-length-to-height ratio in the Japanese may be a specific and epigenetically stable character of Mongoloids acquired after the migration “out of Africa” in the course of dispersion to the north and northeast under severely cold climatic conditions.