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Ancient hominin’s tiny brain raises big questions about human evolution

Scientists were surprised by the modern structure of Homo naledi’s brain.


Artists's reconstruction of Homo naledi (Mark Thiessen/National Geographic/PA)

Artists's reconstruction of Homo naledi (Mark Thiessen/National Geographic/PA)

Artists's reconstruction of Homo naledi (Mark Thiessen/National Geographic/PA)

Brain size may not matter as much as scientists previously thought, a surprise discovery has shown.

The ancient hominin species Homo naledi, that lived in South Africa between 236,000 and 335,000 years ago, had a brain a third the size of ours.

Yet when researchers re-created the shape of the creature’s brain, they found it had an extraordinarily modern structure.

It suggests that, despite having such a tiny brain, naledi may have been capable of language and advanced behaviours such as complex tool making.

The hominin’s remains had already revealed evidence of human-like feet, hands well-suited for tool-making, and teeth adapted to a high quality diet.

Professor Lee Berger, from the University of the Wiwatersrand in Johannesburg, whose team unearthed H naledi in 2013, said: “Archaeologists have been too quick to assume that complex stone tool industries were made by modern humans.

“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.”

The discovery of H naledi at the Rising Star caves in the Cradle of Human Kind world heritage site was hailed as one of the most significant human origin finds of the 21st century.

The creature, a strange mosaic of ape and human features, may have lived alongside early members of our own species, Homo sapiens.

This is the skull I've been waiting for my whole careerDr Ralph Holloway, Columbia University

In the new study, scientists pieced together traces of H naledi’s brain shape from skull fragments belonging to at least five adult individuals.

One fragment bore a clear imprint of wrinkles on the surface of the left frontal lobe.

Lead author Dr Ralph Holloway, from Columbia University in New York City, said: “This is the skull I’ve been waiting for my whole career.”

Naledi’s frontal lobes were similar to those of humans – and very different from those of great apes, the scientists discovered.

Earlier homo human relatives, such as Australopithecus africanus, were much more ape-like in this region – a part of the brain vital to human language.

The back of the brain, including the visual cortex, also showed modern human traits.

The research is published in the journal Proceedings of the national Academy of Sciences.