How Evolutionary Forces, Development Constraints And A Changing Climate Influenced Genetic Drift

It has long been suggested that the relationship between Bergmann (1847) and Allen (1877) ecogeographical principles and geography may be applied to humans. For well over a century, these ecogeographical principles have been used by biological anthropologists to test hypotheses about variation in human body shape and size.

As such, we explored variations in body and limb proportions of the Jomon hunter-gatherers (14,000–2,500 BP), the Yayoi agriculturalists (2,500–1,700 BP) of Japan, and the Kumejima Islanders of the Ryukyus (1,600–1,800 AD) in order to understand the complex interaction of genetic adaptation; development and allometric constraints; selection, gene flow and genetic drift with changing cultural factors (i.e., nutrition) and climate. This assessment will illuminate the complex population history in the Japanese archipelago, which has been frequently discussed in the anthropological literature.

First, the Jomon, the Yayoi, and the Kumejima Islanders were compared with 11 geographically diverse skeletal postcranial samples from Africa, Europe, Asia, Australia, and North America. These geographically diverse populations represented different “climatic zones”: tropical, temperate, and arctic populations. And, the Jomon and Yayoi should cluster with cold-adapted populations, and the Kumejima should cluster with warm-adapted populations.

However, the indigenous Jomon people who were the possible descendants of Late Pleistocene modern humans from Northeast Asia showed morphological mismatch: relatively “wide” body breadths which are cold-adapted body proportions with warm-adapted limb proportions. In fact, Jomon’s brachial index was similar to what one would find in people from tropical climates. The Yayoi rice agriculturalists who were the more recent migrants from Northeast Asia, adhered to the Allen-Bergmann expectation of cold-adapted body and limb proportions.

The Kumejima people who lived in the sub-tropical island in the Ryukyu during the Edo Period was a surprise. Postcranial bone measurements indicated short limb lengths, cold-adapted body proportions and cold limb proportions similar to people who live in higher latitudes and colder climates. But, they exhibited smaller body mass which indicated adaptation to a warmer climate.

In order to explore population history and population structure, this study applied Relethford-Blangero analysis as a measure of the magnitude of genetic drift or gene flow. For instance, Jomon and the middle Yayoi experienced relatively little gene flow, and there was little interregional contact among Jomon-derived indigenous people and Yayoi during the middle Yayoi Period. In contrast, Kumejima had gene flow and migration.

During the Jomon Period, the Japanese archipelago went through postglacial warming from 10,000 BP until 4,300 BP when mean annual temperatures were 3°C higher than the mean annual temperatures today in Japan. It is possible that the late Pleistocene ancestors of Jomon who possessed cold-adapted body may have migrated to the Japanese archipelago from colder Northeast Asia, and a change in limb proportions may have occurred after experiencing the warmer environment of Japan over a considerable amount of time.

The recent genomic studies indicate that the later Jomon people (beginning 3,000 BP) might have more allele sharing with the Yayoi agriculturalists. But, the Yayoi display shorter brachial index and crural index compared to Jomon. According to the results of Relethford and Blangero analysis, lower level of phenotypic variation of the Yayoi might be caused by a founder effect at the time of immigration from the small population size of the initial immigrants.

The physical traits of the Kumejima, cold-adapted body proportions and limb, might be a result of gene flow from “the ethnic Japanese” who were descendants of the Yayoi people after the Medieval Period. The difference between body mass and body proportions/limbs might be caused by allometry or climate and/or nutrition. For nutrition, heat-adapted body mass can mimic nutritional response. According to the history of Okinawa, the Kumejima people from 1,700 AD until 2,000 AD had imposed upon them a heavy tax for crops and textiles. Consequently, the Kumejima people might have experienced nutritional stress which may have influenced their body size.

In conclusion, natural selection may have been the primary force in the interaction of genetic drift and gene flow in the late Pleistocene. In the Holocene, however, genetic drift was probably the primary force combined with gene flow with cultural factors (e.g., diet and nutrition). In the fluctuating climate of the late Pleistocene and Holocene East/Northeast Asia, the mismatch in limb and body proportions may have represented the best compromise in the postcranial adaptive complex.

These findings are described in the article entitled An assessment of postcranial indices, ratios, and body mass versus eco-geographical variables of prehistoric Jomon, Yayoi agriculturalists, and Kumejima Islanders of Japan, published in the American Journal of Human Biology. This work was led by Noriko Seguchi (Kyushu University), Conrad B. Quintyn (Bloomsburg University), Shiori Yonemoto (Kyushu University Museum), and Hirofumi Takamuku (Doigahama Site Anthropological Museum).

About The Author

Noriko Seguchi

Noriko Seguchi currently works at the Faculty of Social and Cultural Studies, Kyushu University. Noriko does research in Biological Anthropology. Their current projects are and '3D data acquisition for bioarchaeology, forensic anthropology, and archaeology contexts' and 'Integrated research into the processes and mechanisms of racialization.'

Conrad Quintyn

I am passionate about science; human prehistory and history; and biological evolution. We humans (with our intelligence) have modified our natural and cultural environment to suit our purposes and this modified environment has impacted our biology, i.e. Agricultural and Industrial Revolutions--the proliferation of infectious and non-infectious diseases. In short adaptation and evolutionary change will be critical in the present environment of "super" microbes. In essence, evolutionary studies and how organisms adapt is quite fascinating to me. My objective is to find a position to study evolutionary change.

Speak Your Mind!


The Levels Of Biological Organization: How The Body Is Organized

The levels of biological organization are the hierarchy of living organisms from simplest to most complex: atoms to molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem and finally biosphere. The human body maintains its life processes at different levels of structural organization. Depending on who you talk to, the exact number of categories […]

Implication Of Global Warming On Electricity Demand In Australia

The increase in temperatures as a result of global warming has serious implications for electricity demand. Global warming, which is an important aspect of climate change, is caused by an increase in greenhouse gases (GHGs) from mostly fuel combustion. As global temperatures increase, there is a paradigm shift in electricity consumption pattern towards cooling demand, […]

New Modeling Techniques Could Be Key To Developing Antibiotics To Combat Superbugs

A new project by researchers at Newcastle University could help in the fight against drug-resistant strains of bacteria. By using a new form of neutron imaging, the team was able to create an extremely accurate model of the interaction between the outer membrane of Gram-negative bacteria and Polymyxin B, a powerful antibiotic. This model provides a valuable way […]

Specialised Cells: Their Function

Cells become specialized so that they can perform a set of particular roles or functions, playing their part in reproduction, energy metabolism, regeneration, information transfer, etc. One of the fascinating areas of study about the human body is cell biology. Cell biology is the study of the microscopic cells (specialized or otherwise) that of which […]

Define Mean In Math

The arithmetic mean of a set of numbers is equal to the sum of that set of numbers divided by the number of elements in the set. As an example, for the set S = {1, 3, 5, 7, 9}, the arithmetic mean of S is equal to (1+3+5+7+9)/5 = 5. The arithmetic mean of a set […]

Climate Change And Estuaries: C, N, and P Retention Fluxes

Estuaries serve many important functions – they provide recreational opportunities for coastal populations, host important fisheries (including oysters, blue crabs, and striped bass), and support a diverse food web that contains species from both the freshwater and marine realms. The mixing of marine and freshwater creates unique conditions and high rates of biogeochemical activity. Ecosystem ecologists […]

Meditation Can Actually Lead To Growth In Certain Regions Of The Brain

A growing interest in the practice of meditation has also spurred a growing body of research on the topic. Recent research done by the Max Planck Institute of Human Cognitive and Brain Sciences, and published in the journal Science Advances, implies that different forms of meditation can improve your brain in different ways. Meditation seems […]