Research press release


Nature Communications

Evolution: African pygmies' stature is set in infancy



今回、Fernando Ramirez Rozziたちは、数百人のバカ族(新生児から25歳まで)を対象とした2つの縦断的研究を実施した。その結果、バカ族の新生児の身長はフランス人集団の身長の標準範囲内にあるが、生後2年間の成長速度が著しく低下することが判明した。Rozziたちは、生後2年間の成長の鈍化によって成長遅延が持続して、そのことが3歳以上のバカ族の子どもの身長に示されていることを明らかにした。しかし、こうした成長の鈍化を除けば、バカ族の人々の成長速度は、他の民族と同じだった。

Two longitudinal studies of the Baka people of West Africa, sometimes referred to as pygmies, show that their small stature is the result of a significant slowdown of growth during the first two years of life, reports a paper published in Nature Communications. This growth cycle differentiates the Baka people, sometimes referred to as pygmies (a term that has been used to describe these populations worldwide though it has no biological foundation), from East African tribes of similar height and suggests convergent evolution in response to a similar environment.

Populations of short average stature show that growth patterns can vary among modern humans, although the mechanisms behind these variations are not well understood. African populations of short average stature share a common ancestor and inhabit similar environments (rainforests), with similar socio-economic and cultural behaviour patterns, suggesting a biological foundation for the African pygmy phenotype. However, when and how the pygmy phenotype is acquired during growth remains unknown.

Fernando Ramirez Rozzi and colleagues conducted two longitudinal studies of the Baka people, involving several hundreds of individuals, from birth to age 25. They found that new-born Baka are within standard size limits for French populations, but that the growth rate slows significantly during the first two years of life. The authors observe that this slowing produces a lasting delay in growth that is evident in the size of Baka children from age 3. Aside from this slowdown, the Baka people’s growth rate continues at a rate similar to other human populations.

doi: 10.1038/ncomms8672

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