Skulls show man's ancestors had ‘ape-like brains'

Humans who walked the earth more than three million years ago had an ape-like brain structure but man-like brain growth, new research reveals.

The findings are based on analysis of eight fossil skulls which show the "hallmark of evolution" as ape and human features merged.

The bones belong to people from the Australopithecus afarensis species - the same group as the famous early human ancestor “Lucy”.

An international team of scientists, which included researchers from the Natural History Museum and University College London, used state-of-the-art scanning technology to examine the ancient skulls collected from archaeological sites in Ethiopia.

Philipp Gunz, a biological anthropologist at the Max Planck Institute for Evolutionary Anthropology in Germany and lead author on the study, said: “Our data show that Australopithecus afarensis had a more ape-like brain, that nevertheless developed over a longer period of time, more similar to modern humans.”

While brains do not fossilise, they leave imprints on the inside of the skull, which can reveal information about the structure and development of the organ.

Analysis of these brain imprints revealed key differences in the structural organisation of human and A.afarensis​ brains.

For example, the team found the placement of the lunate sulcus – a fissure that separates the anterior and posterior parts of the brain – closer to the front of the brain in A.afarensis, like chimpanzees.

In humans, this fissure is pushed further down in the brain.

The researchers calculated the endocranial volume, or brain mass, of an A.afarensis infant and found evidence of a prolonged period of brain development compared with chimpanzees.

They believe the findings show that brain growth in A.afarensis was protracted, suggesting their children, like those of modern humans, had a long dependence on caregivers.

Fred Spoor, a scientist at the Natural History Museum and a co-author on the study, said: “Our new results now show what their brain looked like, and how it grew after birth.”

A.afarensis inhabited East Africa more than three million years ago, and is widely accepted to be ancestral to all later hominins, including humans.

The 3.2 million-year-old ape Lucy was the first A.afarensis skeleton ever found and is considered to be the world’s most famous early human ancestor.

Zeresenay Alemseged, a paleoanthropologist from the University of Chicago in the US and senior author on the study, said: “Lucy and her kind provide important evidence about early hominin behaviour.

“They walked upright, had brains that were around 20 per cent larger than those of chimpanzees, may have used sharp stone tools.”

He added: “Our new results show how their brains developed, and how they were organised.”

The findings are published in the Science Advances journal.

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Skull of 3.8 million-year-old human ancestor discovered in Ethiopia