Geographic variation in body form of prehistoric Jomon males in the Japanese archipelago: Its ecogeographic implications

Abstract

Diversity of human body size and shape is often biogeographically interpreted in association with climatic conditions. According to Bergmann's and Allen's rules, populations in regions with a cold climate are expected to display an overall larger body and smaller/shorter extremities than those in warm/hot environments. In the present study, the skeletal limb size and proportions of prehistoric Jomon hunter-gatherers, who extensively inhabited subarctic to subtropical areas in the ancient Japanese archipelago, were examined to evaluate whether or not the inter-regional differences follow such ecogeographic patterns. Results showed that the Jomon intralimb proportions including relative distal limb lengths did not differ significantly among five regions from northern Hokkaido to the southern Okinawa Islands. This suggests a limited co-variability of the intralimb proportions with climate, particularly within genealogically close populations. In contrast, femoral head breadth (associated with body mass) and skeletal limb lengths were found to be significantly and positively correlated with latitude, suggesting a north-south geographical cline in the body size. This gradient therefore comprehensively conforms to Bergmann's rule, and may stem from multiple potential factors such as phylogenetic constraints, microevolutionary adaptation to climatic/geographic conditions during the Jomon period, and nutritional and physiological response during ontogeny. Specifically, the remarkably small-bodied Jomon in the Okinawa Islands can also be explained as an adjustment to subtropical and insular environments. Thus, the findings obtained in this study indicate that Jomon people, while maintaining fundamental intralimb proportions, displayed body size variation in concert with ambient surroundings.

Metric characteristics of human limb bones in Asian and Japanese populations

“…A southern or northern origin hypothesis of the Jomon people has been discussed on the basis of morphological and genetic studies (Turner, 1987(Turner, , 1989(Turner, , 1990Matsumura and Hudson, 2005;Cavalli-Sforza et al, 1988;Kozintsev, 1990;Omoto and Saitou, 1997;Ishida and Kondo, 1999;Bannai et al, 1999;Tokunaga et al, 2001;Tajima et al, 2004;Tanaka et al, 2004; Komesu et al, 2008;Hanihara and Ishida, 2009;Adachi et al, 2011), but this issue remains unresolved. However, because the long distal segments in the intralimb proportions of the Jomon people are stable from northern Hokkaido to the southern Ryukyu Islands (Fukase et al, 2012), the stability might decrease with the north-south cline of the intralimb proportions in this study. As a last reason, the recent Ryukyu Islanders show very low brachial and crural indices (76.0 and 79.9, respectively), which are comparable to those in northeast Asians.…”

“…Although analysis of variance revealed a significant difference between the samples compared in this study, the crural index (T1:F1) was not significantly correlated with latitude, partly because the Jomon and Ainu peoples were included in this study (Figure 2c). The Jomon and Ainu peoples have very high crural indices among the East Asians, while such indices are low in the Yayoi people, modern mainland Japanese, and Ryukyu Islanders from the same Japanese islands (Yamaguchi, 1989;Temple et al, 2008;Fukase et al, 2012). However, even when the Jomon series was excluded from the analysis, the correlation was not significant.…”

Regional variations in the Jomon population revisited on craniofacial morphology

“…Fukase et al (2012) pointed out the geographical cline of Jomon postcranial metrics, which was recognized as a reflection of Bergmann's law, i.e. a body size difference from north to south in Japan.…”

“…The lengths of the postcranial long bones and the size of the femoral head can be interpreted as a proxy of the body size (stature and body weight). Fukase et al attributed the observed cline of the body size to 'Bergmann's rule'; however, they did not exclude other factors, such as phylogenetic dissimilarity or ad hoc growth differences among the Jomon population (Fukase et al, 2012).…”

“…Postcranial remains of Jomon skeletons have also provided interesting results regarding geographical variation (Fukase et al, 2012). These authors measured the lengths of the humerus, radius, femur, and tibia from the Early to the Final Jomon period and compared them among five regional divisions: Hokkaido, Tohoku, Kanto and Tokai, Kyushu, and Okinawa.…”