Pygmies’ Small Stature Evolved Multiple Times

By Carl Engelking | August 19, 2014 3:23 pm
batwa

Batwa rainforest hunter-gatherer in Bwindi Impenetrable Forest National Park, Uganda.  Image courtesy of George Perry

There are roughly half a million known pygmy people living in various tribes around the world, clustered mainly near the tropics in African and Southeast Asia. Anthropologists have long attributed the small body sizes of pygmy peoples to nutritional deficits resulting from harsh living conditions of the rainforest. But in a new study, researchers report that the human pygmy trait has a genetic basis, and has in fact evolved several times in different populations.

“We have found the strongest evidence yet that the pygmy phenotype is controlled by genetics,” Luis Barreiro, the study’s author, told National Geographic.

Tracking the Genes

Researchers focused on the Batwa pygmy people of Uganda’s Bwindi Impenetrable Forest, comparing them to their taller neighbors, the Bakiga people. The Bakiga were on average 5 inches taller than the Batwa, but they inhabit a similar environment, eat similar food and often intermarry. They collected blood and saliva samples from 169 Batwa adults and 61 Bakiga adults and compared their genomes.

The DNA analysis revealed 16 different genomic locations associated with the pygmy phenotype. These variations were in areas of the human genome that code for human growth hormone and bone formation. Further, the analysis revealed that the effects were cumulative: people with more of the Bakiga genes at these locations were also taller.

Uncommon Ancestry 

Their findings led to another question: Do all human pygmies have a common ancestor? To answer this, researchers took DNA samples from another pygmy tribe in west central Africa, called the Baka. If the pygmy phenotype originated from a common ancestor, then the genomes of the Baka and Batwa would vary in the same ways. However, this was not the case. The two tribes’ pygmy genes were different.

That means that pygmy traits evolved independently in these two different populations, and likely in many different populations around the world. Researchers published their findings Monday in Proceedings of the National Academies of Science.

An Adaptive Trait

Researchers speculate that pygmy mutations were beneficial in a rainforest environment, and so when they arose, they spread. For example, shorter people have an advantage in the rainforest because they generate less body heat, need less food and don’t use up energy repeatedly ducking under myriad vines and branches, researchers say. 

More study will be needed to determine just how environment interacts with genetics to favor a pygmy stature.

And the evidence just goes to show that humans, just like every other creature on this planet, continue to evolve to acquire advantages in our environments.

CATEGORIZED UNDER: Living World, top posts
  • Jeff Shepherd

    People will no longer evolve due to technology. If its to sunny we invent sun-cream. If we find our self to tall for life in the jungle we just cut down the trees. Also people do not look different due to a mutant DNA. They are not a mutated version of the perfect human. Who is to say who, if any one, is to represent perfection.

    • Brett Champion

      I think that overlooks the extent to which technology itself can be a driver of human evolution. Humans that lived, say, 50,000 years ago wouldn’t have been able to thrive the way modern humans do on a diet so heavy in grains. That’s because the very fact that humans started to consume a diet heavy in grains caused an evolution in humanity to better deal with such a diet. That transformation in diet was brought about by the technological revolution of agriculture.

      • Jeff Shepherd

        Not only grain but alcohol and sugar. I was thinking more major changes other than dietary related ones. Life and the environment does not kill off people because we can invent ways to prevent this from occurring.

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