Published on 6 August 2015
Research

The growth mechanisms of these small men decrypted.

A team of researchers from CNRS, IRD and the UPMC and the Centre for Research in Epidemiology and Population Health (Inserm / Université Paris Sud / UVSQ) studied, to decrypt these growth mechanisms, a group of pygmies Baka, Cameroon. Their results show that they grow to a completely different rhythm of another pygmy group, despite similar adult size, which means that the small size appeared independently in both sets.

The size of the Pygmies plot  Westerners since they first met in 1865. This people is actually composed of several ethnic groups, grouped into two sets. They all live in the forest, in connection with Bantu farmers.

The researchers showed that if the Baka are born with standard measurements, growth slowed sharply until the age of three years. Their growth curve then runs parallel world standards, with a growth spurt in adolescence and reached adult size average at the same time as the rest of the planet. However, they do not catch up their delay. For their part, the Pygmies is born with a reduced size. Their small stature is after different growth process Baka.

The morphology of these pygmy populations stems from two different mechanisms, which could be related to an imbalance between growth hormone and the two IGF2 hormones, and that allowed them to adapt to the rainforest. This is called convergent evolution.
 
Pygmy these groups are separated there are between 8000 and 13 000 years, which shows that human growth can progress in a relatively short time. This plasticity of growth could play a decisive role in the expansion of Homo sapiens outside Africa, allowing it to adapt quickly to new environments.
 
This work was published July 28, 2015 in Nature Communications.