One particular hallmark of contemporary human biology is that our skulls and brains are both globular. As a new study has recently concluded, however, it appears that modern humans who are carriers of very specific Neanderthal DNA may actually have much less round heads than others without this DNA.
According to Science Daily, the new study on Neanderthal DNA has helped scientists to better understand how human brains and skulls have evolved over thousands of years. Philipp Gunz, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology, conducted the recent study on the evolution of human brains. He was joined by Amanda Tilot of the Max Planck Institute for Psycholinguistics. Gunz explained that very subtle differences, but differences nevertheless, were demonstrated in the endocranial shape of humans.
"We captured subtle variations in endocranial shape that likely reflect changes in the volume and connectivity of certain brain areas."Because humans that have European ancestry also share a certain percentage of their DNA with Neanderthals through previous interbreeding, Tilot, Gunz, and other scientists involved in the new research took a look at the cranial shape of modern humans by studying MRI brain scans -- while also analyzing the Neanderthal DNA of 4,500 people.
After analyzing tomographic scans, scientists were able to work out how endocranial shape may have differed between Neanderthals and modern humans. They further looked at chromosomes 1 and 18, chromosomes that were found in Neanderthal DNA and which still reside in human physiology today. Said chromosomes were linked to skulls that were far less round than they would have been without this Neanderthal variant.The Neanderthal DNA fragments that were analyzed featured two specific genes which are very important for brain development. Namely UBR4, which is linked to neurons, and PHLPP1 -- which is linked to the creation of myelin insulation which occurs at the location of nerve cell projections.
As senior author Simon Fisher, a geneticist at the Max Planck Institute for Psycholinguistics, noted, "We know from other studies that completely disrupting UBR4 or PHLPP1 can have major consequences for brain development. Here we found that, in carriers of the relevant Neanderthal fragment, UBR4 is slightly down-regulated in the putamen. For carriers of the Neanderthal PHLPP1 fragment, gene expression is slightly higher in the cerebellum, which would be predicted to have a dampening effect on cerebellar myelination."
Fisher further added that while certain Neanderthal DNA in modern humans has been shown to produce less of a globular brain shape than would be true for those without this Neanderthal DNA, the difference is one which should still be understood and appreciated.
"The Neanderthal variants lead to small changes in gene activity and only push people slightly towards a less globular brain shape. This is just our first glimpse of the molecular underpinnings of this phenotype, which is likely to involve many other genes."The new study on how Neanderthal DNA has affected the shape of the skulls and brains of contemporary humans has been published in Current Biology.