Our Ancestors First Developed Manual Dexterity, Started Walking Upright Sometime Later

Early hominids first figured out how to use tools, and only later on “decided” to switch from walking on all fours to walking upright, a new paper in the journal Philosophical Transactions of the Royal Society B argues.

The researchers now stating that, contrary to popular opinion, manual dexterity preceded the emergence of bipedal locomotion, base their claims on data collected while using MRI machines to scan the brains of both human volunteers and monkeys.

More precisely, the scientists made use of magnetic resonance imaging to pin down the areas of the brain in charge of touch awareness in each finger and toe both in the case of humans, and in the case of monkeys.

This allowed them to put together so-called somatotopic maps, which basically show the neural locations of single digits in the hand and foot. In the case of monkeys, all toes share a single map. In the case of humans, the big toe appears to stand on its own.

According to the researchers, this means that early hominids got dexterous fingers while they were still quadrupeds, and, as they came to perfect their manual dexterity, they also switched to bipedal locomotion.

“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 researchers write in their paper, as cited by Riken.

“Evolution is not usually thought of as being accessible to study in the laboratory, but our new method of using comparative brain physiology to decipher ancestral traces of adaptation may allow us to re-examine Darwin’s theories,” Dr. Atsushi Iriki from the University of Tokyo Museum wished to stress.

By the looks of it, this hypothesis is backed up by data collected while studying the 4.4-million-year-old fossilized remains of a quadruped hominid belonging to a species dubbed Ardipithecus ramidus.

Thus, this species appears to have had hand dexterity despite the fact that it roamed the Earth before the human-monkey lineage split.