The Tiny Brains Of An Extinct Human Ancestor Looked Remarkably Like Our Own

The early hominin is much smaller than modern humans, but have strikingly similar brains. John Hawks

When researchers announced the discovery of Homo naledi in South Africa a few years back, the primitive looking hominin rocked the anthropological world. But now researchers are suggesting that despite appearances, the small hominins' brains were remarkably similar to our own, raising questions about their intelligence.

The researchers were able to reconstruct what the brain of the long-extinct hominin looked like due to the astonishing wealth of Homo naledi fossils – and their incredible condition – that have been found in the cave system. This includes a number of fossil skulls that still record parts of the imprint of the brain on the inside, known as an endocast, which has allowed the researchers to piece together a cast of the creatures’ entire brain.

Now obviously this cannot reveal what was going on in the middle of the noggin, but it can give the scientists studying it some clues as to the surface of the brain, and allow them to compare it to our own. One skull fragment, for example, displayed astonishingly clear imprints of the brain’s left frontal lobe.  

The endocast of H. naledi shows a well developed frontal lobe. Heather Garvin

The result indicates that despite Homo naledi being thought of as an ape-like animal in appearance, their brains looked remarkably more like modern humans than chimpanzees. When then compared against other members of the genus, such as Homo erectus, Homo habilis, and even the tiny Homo floresiensis “hobbits”, and it is clear that they all have very similar frontal lobes to what is seen in us. Conversely, earlier ancestors such as Australopithecus africanus had a brain more similar in shape to apes.     

“It's too soon to speculate about language or communication in Homo naledi,” explained co-author Shawn Hurst, “but today human language relies upon this brain region.”

We’re used to thinking that it was our big brain that gave us our smarts and helped to propel our ancestors to the top of the food chain. But this latest work adds to the growing body of evidence that it is not the size of the brain that matters, but more the morphology and chemistry within it that is most important.

If this is shown to be right, then it could have some serious implications for how we have previously interpreted artifacts. Recently it was suggested that cave paintings in Europe might predate the arrival of modern humans, implying that Homo neanderthalensis created them and possibly casting doubt on who made other prehistoric works of art.

“Archaeologists have been too quick to assume that complex stone tool industries were made by modern humans,” said Lee Berger, who is credited with first identifying H. naledi. “With naledi being found in southern Africa, at the same time and place that the Middle Stone Age industry emerged, maybe we've had the story wrong the whole time.”

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