Researchers have overturned the widespread theory that dexterous hands evolved after bipedal locomotion was already developed.
The research team used functional magnetic resonance imaging on humans and electrical recordings from monkeys to pinpoint the part of the brain responsible for processing touch sensations in each finger and toe, a RIKEN press release reported.
The team made visual representations of their findings called somatotopic maps. The team found that both monkey and human's small toes can be fused into a single map, the difference is the human big toe can has its own map that is not found in monkeys.
This finding suggests ancient hominids developed dexterous fingers while they were still walking around on all fours.
"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 study authors wrote, according to the press release.
The researchers were able to study the early brain development by analyzing the bones of a 4.4 million-year-old hominid Ardipithecus ramidus specimen. The being walked on four legs and had hand dexterity that "preceded the human-money lineage split."
"The findings suggest that the parallel evolution of two-legged locomotion and manual dexterity in hands and fingers in the human lineage were a consequence of adaptive pressures on ancestral quadrupeds for balance control by foot digits while retaining the critical capability for fine finger specialization," the press release reported.
The new research methods could help researchers change the ideas of evolution as we know it.
"Evolution is not usually thought of as being accessible to study in the laboratory," study leader and neurobiologist Doctor Atsushi Iriki, said. "But our new method of using comparative brain physiology to decipher ancestral traces of adaptation may allow us to re-examine Darwin's theories".
