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.