This is Scientific American 60 Second Science.

I'm Cynthia Graber.

Got a minute?

The term Pygmy usually refers to a few groups of short-statured people in equatorial

rainforest regions in Africa.

The existence of distinct populations of such people presented scientists with the opportunity to study the mechanisms

by which typical human growth patterns have become altered there,

and they discovered that two groups became small in two different ways.

The studies in the journal Nature Communications.

The researchers collected data on some 500 members of a West African ethnic group called the Baca. This during their first two years which produces a lasting effect.

This mechanism seems to be different from that of East African groups called the Efei and the Sua.

These peoples have slow prenatal growth so that the infants are born smaller.

The researchers say that the Baca population

appears to have split from the Efei and Sua

some 20,000 years ago.

The two different systems for achieving small stature,

which appears to be advantageous

in the equatorial rainforest environment, thus an example of convergent evolution.

The researchers believe the findings say something important about human evolution and development in general,

quote, Homo sapiens could therefore be characterized

by its high capacity for growth plasticity during infancy.

This capacity, which may be unique to our species,

...