Short-statured people known as pygmies live in rain forests around the world, and a new study puts forth a relatively simple explanation for their height: Their shorter step lengths make it a lot easier for them to walk around in dense jungles than it is for taller people. As Newsweek explains, scientists have never been able to settle on why males with the pygmy phenotype tend to max out at 5-foot-2 and women at shorter heights. But after studying the Batek of Peninsular Malaysia and the Tsimane of the Bolivian Amazon, researchers make their case in the Proceedings of the Royal Society B that "locomotor performance" is the driving factor. The pygmies' shorter height results in shorter steps that facilitate more efficient foraging, and the researchers theorize that jungle populations evolved over the eons to take advantage of the trait, per a post at Phys.og.
"It is highly intuitive—anyone who has trekked off-trail in a rainforest knows how difficult it is," says Vivek Venkataraman of Harvard’s Department of Human Evolutionary Biology. "Especially if you are tall, you feel extremely clumsy. But for people who live in these environments, it seems easy for them to move around." The researchers speculate that other factors may be at play, though they haven't been fully explored yet. For example, the bodies of people with a smaller stature may be able to dissipate heat better, which would be an advantage in a rain-forest climate. They also note that the phenomenon isn't specific to humans—other large mammals who live in rain forests are typically smaller than their counterparts elsewhere. (For pygmies in the Congo, marijuana can be a life-or-death crop.)