Human Genetics: The Growth Rate of Pygmies

The stature of pygmies is well-suited to tropical rainforests, but the mechanisms underlying their growth remain poorly understood. Now, researchers have taken a closer look at volunteers from a group of Baka pygmies in Cameroon to better understand their growth rate.

The stature of pygmies has long intrigued Westerners since their first encounter with them in 1865. This population of people is actually made up of several ethnic groups which belong to two main clusters. One is spread across Equatorial West Africa while the other is found in East Africa.

While genetic factors are responsible for the small stature of pygmies, until now researchers were unable to produce reliable data on their age in order to analyze growth patterns. Now, thanks to the registers of the Catholic mission in Moange-le-Bosquet, Camaroon, researchers managed to look at 500 members of the Baka ethnic group for eight years in order to establish the first growth patterns for pygmies.

The body size at birth for this group was within normal limits. However, growth then slowed significantly until the age of three years. The growth curves then paralleled the global standards, with a growth spurt at adolescence and an adult size achieved on average at the same time as that seen throughout the world.

What's interesting is that pygmies in the western cluster experience this particular type of growth. However, pygmies in the eastern cluster were born with a smaller body size, so that their small stature resulted from growth processes different from those of the Baka. This means that the pygmy morphology of these populations results from two different mechanisms.

The findings reveal that since these pygmy clusters split apart between 8,000 and 13,000 years ago, humans have the ability to evolve relatively rapidly within a short period of time. This growth plasticity may have played a determining role in the spread of human outside Africa, allowing them to adapt rapidly to new environments.

The findings are published in the journal Nature Communications.

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