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The brain of the mysterious ‘foot’ of human relative was a half-man, half-monkey

In a recent study, the researchers compared the skull of the Small Foot (shown here) with those of other hominins.
(Photo courtesy of the University of the Witwatersrand)

The brain of one of the oldest Australopithecus persons ever found, was a bit like that of monkeys, and a little bit human.

In a new study, researchers scanned the interior of a very rare, nearly complete skull of this ancient hominin ancestor. Hominins include modern and extinct humans and their immediate ancestors, such as Australopithecus, who lived between roughly 4 million and 2 million years ago in Africa, and the early humans of the genus Homo would eventually evolve from Australopithecine ancestors.

The modern human brain has a lot to owe to this little, furry ancestors, but we know very little about their brains, said Amélie Beaudet, a paleontologist at the University of the Witwatersrand in South Africa. [Photos: ‘socket’ Human Ancestor Walked with Lucy]

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Beaudet and her colleagues used micro-computed tomography (micro-CT), a highly sensitive version of the same kind of technology that a surgeon could use to scan a bum knee. With this tool,the researchers reconstructed the inside of the skull of a very old Australopithecus.

The skull belongs to a fossil called “Little Foot” first two decades ago in the Sterkfontein Caves near Johannesburg. At 3.67 million year old Little Foot is one of the oldest of an Australopithecus ever found, and his skull is almost intact. The fossil of the discoverers think that it belong to a whole new Australopithecus species, Live Science reported.

With micro-CT, the research team could see very fine imprints of where the brain once lay at Little base of the skull, including a registration of the paths of veins and arteries, Beaudet told Live Science. With the help of the skull off of the brain form in this way is called the making of an endocast.

“I was expecting something very similar to the other endocasts that we knew from the Australopithecus, but Little Foot was a bit different, in accordance with his age,” Beaudet said.

Today’s chimpanzees and humans share an ancestor that is older than Little Foot: a number of long-lost monkey that gave rise to both sexes. Base of the brain is similar to that predicted ancestor should look, Beaudet said, more monkey than man. Little Foot from the visual cortex, in particular, took a greater part of the brain than that area in the human brain.

In humans, Beaudet said, the visual cortex is cast aside to make room for the expansion of the parietal cortex, an area involved in complex activities, such as toolmaking.

The change of the brain

Base of the brain is asymmetric, with a slightly different protrusions on each side, the researchers found. This is a feature shared with both humans and monkeys, and likely indicates that the Australopithecus had the lateralisation of the brain, which means that the two sides of the brain performed different functions. The discovery means that the lateralisation of the brain evolved very early in the primate lineage. [Gay Naledi in Pictures: Images of the cerebellum the Human Relative]

Base of the brain was different from later Australopithecus specimens, Beaudet said. The visual cortex, in particular, was larger than the later Australopithecus brain. These differences suggest that the brain’s evolution was a fragmented process, in fits and starts on the other side of the brain.

The findings appear in a special issue on Little Foot is published in the Journal of Human Evolution.

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Originally published on Live Science.

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