How the shape of your skull can reveal Neanderthal DNA

Modern humans with slightly elongated skull shapes may share rare genetic material inherited from Neanderthals, our closest extinct relatives, new research suggests.

Scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have identified Neanderthal DNA fragments in modern human chromosomes 1 and 18 that are linked with less round brains.

The study, described in a paper published in the journal Current Biology, found that the Neanderthal DNA only makes up around 1% to 2% of the total of any modern European human. The effect on the shape of the skull is “too small to be seen with the naked eye, but shows up on brain scans”, New Scientist reports.

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Senior study author Professor Simon Fisher described the effects of the DNA on the skull as “very subtle”, but added that the team had detected them across a large sample size of nearly 4,500 MRI brain scans of European subjects. Scientists believe the genetic material was passed down through multiple episodes of interbreeding between humans and their Neanderthal cousins.

“The Neanderthal variants lead to small changes in gene activity and only push people slightly towards a less globular brain shape,” Fisher explained.

However, the researchers also noted that both of the brain regions in which the Neanderthal fragments were discovered - UBR4 and PHLPP1 - are involved in key functions such as learning and coordinating movements, reports The Independent.

“We know from other studies that completely disrupting UBR4 or PHLPP1 can have major consequences for brain development,” Fisher said.

But as The New York Times points out, the study “wasn’t designed to determine how Neanderthal genes influence thought”, and the researchers stressed that there is currently no indication that the DNA pieces have any effect on the cognitive abilities of modern humans.

“The focus of our study is on understanding the unusual brain shape of modern humans,” said Dr Philipp Gunz, another Max Planck Institute scientist. “These results cannot be used to make inferences about what Neanderthals could or could not do.”

All the same, the study could result in future research to look for more Neanderthal DNA linked with modern human brains and “determine what specific effects these ancient genetic variants might have” by growing brain tissue containing the DNA in a laboratory, adds specialist news site Live Science.