It’s not another tall tale: Evolutionary biologists have developed a new understanding of the genetic basis of short stature in humans. Also known as the pygmy phenotype, a study published Monday in the Proceedings of the National Academy of Sciences shows that this trait has evolved several times over the course of human history.
“We have found the strongest evidence yet that the pygmy phenotype is controlled by genetics,” said Luis Barreiro of the University of Montreal and the senior author of this recent study. Although height is a tremendously variable trait among humans, several rain forest-dwelling populations in Asia and Africa have been noted for their unusually short stature. The average height among Batwa men (60.1 inches, 152.9 centimeters) and women (57.4 inches, 145.7 centimeters) is significantly lower than in neighboring Bakiga men (65.1 inches, 165.4 centimeters) and women (61.0 inches, 155.1 centimeters).
Barreiro and colleagues gathered genetic data from the Batwa and Baka peoples, as well as from three neighboring agricultural groups of average height. When they scanned different regions of the genome, they found significant genetic differences among the Batwa and Baka in an area of the genome that is known to code for the receptors for human growth hormones. When the researchers looked more closely, they found that these genetic differences weren’t just random chance and that the first Batwa and Baka people just happened to be short. Instead, these genetic differences were somehow benefiting the individuals living in these rain forest environments. It’s an example of convergent evolution, Barreiro says, in that the same trait (short stature) evolved independently in several different populations.
The results will help provide an understanding not just of the pygmy phenotype, but also of the evolution of the tremendous amount of diversity in our species.