Two to four percent of the DNA of today’s Europeans and Asians comes from Neanderthals. Now, researchers have discovered neanderthal genes that affect brain development of modern humans.
One of the unique biological traits of modern humans is definitely the head. In comparison to earlier human species like the Neanderthals, we have an unusually round skull shape. Scientists assume that the “round head” in our ancestors was slow to develop and that it reflects significant changes in the brain organization. Perhaps even specific connections of different brain areas and thus also cognitive abilities are related to the changed head shape.
An international team of researchers has now begun to search for genes and biological mechanisms that may have played a role in this transformation. As the scientists report in the journal “Current Biology”, they not only found remarkable differences between people living today, they also came across DNA fragments of Neanderthals, which still have an influence on our individual skull shapes.
Geneticists have known for sometime that many of us carry a bit of Neanderthals. Genome comparisons have revealed that between one and four percent of the DNA of today’s Europeans and Asians originate from the Homo neanderthalensis — our ancestors mated with Neanderthals more than 30,000 years ago. Of course, not everyone carries the same gene fragments, so researchers estimate that a total of 40 percent of the Neanderthal genome distributed across non-African populations has survived to date.
This circumstance was exploited researchers Philipp Gunz from the Max Planck Institute for Evolutionary Anthropology in Leipzig. First, using computer tomography, they used fossils to create virtual impressions of the skull of Neanderthals and modern humans. Using hundreds of measuring points, the scientists were able to record and compare the shape of the respective brain skulls.
Then they used MRI brain scans to examine the inner skull shape of several thousand living humans. The interim conclusion: all of the Homo sapiens brain skulls are significantly different from those of the Neanderthals. That in itself was not very surprising. However, there are also significant differences in shape between today’s modern people.
Altered gene activity
In the next step, the researchers searched the genetic material of the study participants for Neanderthal DNA, which could be relevant in this context. In fact, on chromosomes 1 and 18, they discovered the genetic fragments of our extinct cousins, which are likely to be associated with a more elongated head shape. As it turns out, they also alter the activity of the UBR4 and PHLPP1 genes, which in turn play a role in brain development.
Among other things, UBR4 is involved in the formation of nerve cells in the cerebral cortex. PHLPP1 is involved in the development of the so-called myelin sheath, a protective layer of nerve cell processes. “The effects of these rare Neanderthal DNA fragments are subtle but detectable by sample size,” says study co-author Simon Fisher of the Max Planck Institute for Psycholinguistics in Nijmegen, adding: “This is just the first look at the molecular foundations of brain shape. Like other aspects of the brain structure, the rounded shape is a feature that is likely to be influenced by the combined effects of many different genetic variants.”
However, the current study does not allow any conclusions to be drawn regarding the mental abilities of Neanderthals, emphasize the scientists. “Our focus is solely on exploring the unusual brain shape of modern humans,” says lead author Gunz, while warning against another misinterpretation: the results would not mean that modern-day humans with longer heads are genetically “more Neanderthals” than others. In any case, there are already some indications as to what consequences the genetic heritage of Neanderthals might have: scientists suspect that the higher susceptibility of Europeans to cardiovascular problems compared to Africans is due to their more effective antiviral abilities.