Despite their diversity, pygmies of Western Central Africa share recent common ancestors

February 5, 2009

Despite the great cultural, physical, and genetic diversity found amongst the numerous West Central African human populations that are collectively designated as "Pygmies," a report published online on February 5th in Current Biology finds that they diverged from a single ancestral population just about 2,800 years ago.

The new study is the first to reconstruct the history of the numerous forest-dwelling pygmy populations, who make their livings as hunter-gatherers, and their immediate sedentary, agriculturalist neighbors, according to the researchers.

"The common origin of all pygmy populations from Western Central Africa is de facto assumed by the use of the generic term 'pygmy'," said Paul Verdu of Musée de l'Homme in Paris. "However, due to the lack of archaeological data, such a common origin had never before been assessed. Now, we have shown using genetic data that—despite the fact that there is no such thing nowadays as a pygmy civilization or identity and despite their great cultural heterogeneity—Western pygmy populations in fact do share a common origin and recently diverged from one another."

Nevertheless, pygmy populations today do not know about one another, and they have no myth or story about their own origin, Verdu emphasized. In fact, pygmies do not call themselves "Pygmies." Rather, they identify themselves as distinct ethnic groups, including Kola, Baka, Efe, or Nsua, to name a few. There is also no pygmy language. All pygmy populations speak the language of their non-pygmy neighbors, representing two different language families in Western Central Africa.

Although archeological remains attest to the presence of people in the Congo Basin since at least 30,000 years ago, the demographic history of those groups had remained widely unknown, Verdu said. Scientists also debate about whether pygmies' characteristically short stature is the result of shared history or convergent adaptation to the forest environments in which they live.

In the new study, an interdisciplinary team of researchers including ethnologists and geneticists explored those questions by conducting genetic analyses on 604 people from 12 non-pygmy and 9 pygmy groups in Western Central Africa. They found that the most likely historical scenario to explain the genetic evidence points toward a unique ancestral pygmy population that diversified about 2,800 years ago, perhaps as a result of social constraints imposed on pygmies as non-pygmy agriculturalist populations expanded.

Their analysis showed a high level of genetic diversity among Western Central African Pygmies and evidence for variable levels of intermarriage between pygmy and non-pygmy groups that are consistent with known sociocultural barriers. In fact, Verdu said that the recent and heterogeneous gene flow from non-pygmies into various pygmy populations may have driven the rapid genetic diversification found amongst today's pygmies.

Source: Cell Press