The nearly complete brain of the ancient human relative "Little Foot" shows this ancient hominin had a small brain with a combination of ape-like and human-like features.

One Of The Oldest Australopithecus Ever Found

Hominins include modern and extinct humans and their direct ancestors, which include the Australopithecus that lived in Africa about between 2 million and 4 million years ago.

Findings of a new study now shed more light on these small and hairy beings early humans of the genus Homo are believed to have evolved from.

Little Foot lived about 3.6 million years ago and is among the oldest of Australopithecus ever found. The teeth, face, and pelvic structure of the fossil suggest that the hominin was a young girl, who stood just 4 feet and 4 inches tall. The fossil was first found in Sterkfontein Caves near Johannesburg nearly two decades ago.

Amélie Beaudet, a paleontologist at the University of the Witwatersrand in South Africa used Micro-CT, a more sensitive version of the same technology used in hospital CT scans, to take a closer look at the interior of the nearly complete skull of Little Foot.

Little Foot's Brain

The scans revealed the fine imprints where the brain once lay against the hominin's skull, showing the paths of the veins and arteries. This process of using the skull to infer the brain shape is known as making an endocast.

"I was expecting something quite similar to the other endocasts we knew from Australopithecus, but Little Foot turned out to be a bit different, in accordance with its great age," Beaudet said.

Modern humans and chimpanzees share an ancestor older than Little Foot, a long-lost ape that gave rise to these two lineages. The brain of Little Foot looks similar to how that ancestor's brain is predicted to look like, which is more ape-like than human. The visual cortex of Little Foot took up more proportion of the brain than it does in the human brain.

"In human evolution, when know that a reduced visual cortex, as we can see in our own brain, is related to a more expanded parietal cortex - which is a critical cerebral area responsible for several aspects of sensory processing and sensorimotor integration," Beaudet said. "On the contrary, Little Foot has a large visual cortex, which is more similar to chimpanzees than to humans."

Brain Lateralization

The hominin's brain was asymmetrical with slightly differing protrusions on the sides, a feature shared with both humans and apes. This possibly suggests that the two sides of the Australopithecus' brain performed different functions.

The findings mean that the so-called brain lateralization, the tendency of the different halves of the brain to do things differently, evolved very early in the primate lineage.