Humans Evolved Finger Control Before Learning How to Walk

Human ancestors learnt to control fingers and even make primitive tools before figuring out how to walk on two legs. A new study has overturned the common assumption that humans evolved manual dexterity before evolving bipedalism.

Neurobiologists at the RIKEN Brain Science Institute resolved this long-standing mystery in human evolution by looking at brains of both monkeys and humans (modern and ancient) and comparing their behaviour. The study was led by Dr. Atsushi Iriki and included Dr. Gen Suwa, an anthropologist from the University of Tokyo Museum.

For the study, researchers hooked monkeys and human to functional MRIs scanners and observed the brain areas responsible for touch awareness in both hands and legs. They used electrical signals to create somatotopic maps.

According to Girrardin.org, a Somatotopic Map is explained as "An associative area of the brain that performs a topology preserving mapping of sense organs on the somatosensory cortex."

Using these maps, researchers confirmed that each digit has a discrete neuronal location in both monkeys and humans.

In monkeys, all toes have one somatotopic map, but in humans the big toe has its own map. This difference in monkey and human foot shows that humans first evolved manual dexterity before adopting bipedalism.

"In early quadruped hominids, finger control and tool use were feasible, while an independent adaptation involving the use of the big toe for functions like balance and walking occurred with bipedality," the authors explained.

The study also shows that it is possible to use comparative brain physiology to understand evolution.

"Evolution is not usually thought of as being accessible to study in the laboratory", stated Dr. Iriki in a news release "but our new method of using comparative brain physiology to decipher ancestral traces of adaptation may allow us to re-examine Darwin's theories".

The study is published in the journal Philosophical Transactions of the Royal Society.