Ugandan pygmy tribe display flexible footwork skills
Ankles indicated to give them their extraordinary climbing ability
Scientists from Dartmouth College, Hanover, recently focused on the ankle-flexibility of pygmy populations in Uganda. They filmed the honey-gathering behaviourof pygmies to measure the flexibility of their ankle joints.
The findings, reported in The Proceedings of the National Academy of Sciences, show that pygmy hunter-gatherers have extraordinarily flexible ankles. This enables them to climb up trees with their shins almost touching the trunk, like a chimpanzee. If a person unaccustomed to climbing bent their foot to such extremes, they would suffer severe damage.
The team used ultrasound to compare the length of leg muscle fibres in the Twa of Uganda, a pygmy tribe, with those found in the Bakiga, Ugandan farmers who seldom climb trees. They found that the fibres running alongside the shin bone were much longer in the Twa.
The pygmy climb trees mainly to collect honey, a vital component of their diet and an indicator of social prestige. But climbing and foraging at such heights, in excess of fifty metres, is extremely dangerous. Among the Aka, a nomadic pygmy tribe, falls from trees account for seven per cent of male deaths.
Safe, quick climbing could have acted as the selection pressure driving unusually flexible ankles. These findings have important implications for human evolution. About five million years ago, ancestral humans started walking about on two feet, but exactly what drove this milestone in human development has long been debated. From studying the fossil record, some anthropologists believe that early hominids were incapable of climbing trees because of their foot structure. This has led to the over-simplified classification of dividing human ancestors into two groups: those that swung through the forests and those that stalked the open plains. However, with the discovery of an ankle adapted for life in the trees in modern humans, the situation becomes a touch more perplexing.
