Human standing represents one of the first events in the evolutionary divide between humans and chimpanzees and allowed us to free our hands, although its selective basis is a mystery.
A hypothesis has recently been proposed that links hair loss within the hominin lineage with the inability of babies to cling to their mothers, requiring mothers to walk upright to carry their babies . However, one question remains for this model: what caused the hair loss that resulted in walking upright?
Hairs and ticks
As this study suggests, the reason could be based on the proliferation of ticks, selecting hair loss in hominids and grooming behavior in chimpanzees as divergent strategies against them.
It is then argued that these divergent strategies against ticks resulted in different methods of carrying babies, driving the locomotor divergence of humans and chimpanzees. Specifically, human ancestors lost their hair, and began to walk upright to protect their children . Chimpanzee ancestors, however, tended to use grooming for protection, and had their babies on their backs to walk quadruped.
A great advantage of standing is that it allowed us to save energy when moving around . For that reason, a chimpanzee barely walks 2 to 3 kilometers a day .
At the same time, as Charles Darwin has already observed, freeing the hands thanks to standing, together with the increase in the size of the brain, also facilitated the manufacture of tools, cognition and even language. However, bipedalism also came with some drawbacks, such as back pain – our spine is not well designed for bipedalism, so we are a species that tends to suffer from persistent low back pain.
Ultimately, hominids, in order to increase their intelligence, paid a high price. A constellation of advantages / disadvantages that contributed to the increase in the size of our brain and its density of connections. A series of tributes that you can explore in more depth in the following video :