(CNN) – People have unusually dome (or round) skulls and brains compared to our ancient ancestors, including our closest extinct cousins, Neanderthals, and a new study gives a possible explanation of why.
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For the first time, the team of interdisciplinary scientists has identified two genes that affect the shape of a modern human skull and come from Neanderthals.
"The billions of people living today in their genome are a small part of the Neandertal gene, a distant echo mix when our ancestors left Africa and met Neanderthals," said Philipp Gunz, a paleoanthropologist from the Max Planck Institute for Evolutionary Anthropology. Leipzig, Germany, by e-mail.
They are usually people who have a European origin, derived from the Neanderthal and today's European cross.
"By combining fossil, genetic and brain image data, we can learn something about changes in the evolution of brain development in our own species," Gunz said.
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The team used magnetic resonance imaging to analyze the brain shape of nearly 4,500 people before their genome was searched to find out which Neandertal DNA fragments they carry.
They also studied fossil skulls and ancient genomes to calculate the shape of neanderthal and modern human skulls, and then analyzed whether a particular gene was associated with a less globular brain form in those who performed them.
They found two gene variants that have a negligible effect on the shape of the skull, chromosomes 1 and 18, which after a break affect brain development.
"It gives us our first idea of how genes could contribute to this particularly striking aspect of our anatomy," said Planck Max, Director of Psilinguistic Institute, one of the study's leaders.
The genetic variants found in chromosomes 1 and 18 relate to the expression of two adjacent genes, UBR4 and PHLPP1, that affect the formation and isolation of new nerve cells.
"We would like to understand more about globularity, as this could be due to specific changes in the production of our original, the relative size of different parts of the brain and their interrelation with our ancestors," adds Gunz.