Neanderthal habits
Neanderthal genes in modern humans may increase the risk of addiction
Julia Tisler, ERR
Some gene variants inherited from Neanderthals influence smoking, alcohol consumption and sleep habits of modern humans. According to a recent analysis, in the worst case, they can also increase the likelihood of developing brain disorders.
Disorders, including neurological or mental illnesses, occur in some families more often than in others. The factors contributing to their occurrence are partly hereditary, and in the course of research, scientists have already identified a number of genetic causes of the risk of these diseases. At the same time, it remained unclear why evolution had not eliminated the gene variants that increase the risk of such diseases.
The mystery was solved by studying ancient DNA, including the genetic material of Neanderthals. When modern humans migrated from Africa more than 60,000 years ago, they encountered and mixed with other archaic humans such as Neanderthals. Today, every non-African carries about two percent of the genetic heritage of Neanderthals.
To investigate the links between Neanderthal DNA and behavioral traits of modern humans, an international working group led by researchers from the University of Tartu, Charite University Hospital in Berlin and the University Hospital of Amsterdam analyzed data from the UK Biobank. In total, more than a hundred brain disorders and behavioral habits associated with sleep, smoking or alcohol were studied.
It turned out that Neanderthal DNA is most strongly associated with smoking, alcohol consumption and sleep habits. However, scientists have not found a clear parallel between the DNA of our relative and the risk of brain diseases: Neanderthal DNA does have more than expected associations with signs associated with diseases of the central nervous system, but the diseases themselves were not significantly related to the DNA of this extinct species.
Studies have mainly shown that sleep disorders and alcohol and nicotine use are often risk factors for various neurological and mental disorders.
When studying the data of residents of Estonia, the Netherlands, Finland, Japan and Iceland, the results were confirmed. Two smoking-related gene variants inherited from Neanderthals should be noted separately, which were found in the data of British and Japanese biobanks. "The results show that Neanderthals carried several gene variants that significantly increase the risk of smoking in modern humans," said Michael Dannemann, lead author of the study, associate professor of evolutionary and Population Genomics at the University of Tartu.
However, according to the researchers, it is impossible to say how the same variants affected the behavior or health of the Neanderthals themselves. "The results provide interesting material for further investigation of the exact effects of these genes and, hopefully, will help us better understand the biology of Neanderthals in the future," added Dannemann.
"The significant links of Neanderthal DNA to alcohol use and smoking habits can help us understand the evolutionary origin of addictions and reward—oriented behavior," said Stefan M. Gold, a professor of neuropsychiatry at the Charite Hospital in Berlin, one of the study's leaders.
On the other hand, some anthropological evidence suggests that hunter-gatherers who tolerated these types of substances better had social advantages. "Thus, our results support the hypothesis that it is not brain diseases themselves that have evolutionary advantages, but natural selection that forms the traits associated with them that make us vulnerable to them today," Gold suggested.
Dannemann noted that Neanderthals inhabited parts of Eurasia for more than 100,000 years before modern humans migrated from Africa. "The high frequency of some variants associated with different sleep patterns may indicate that they were useful outside of Africa — in environments characterized, for example, by different seasonality and levels of UV radiation compared to the environment in which modern humans evolved," he said.
The results were published in the journal Translational Psychiatry (Dannemann et al., Neandertal introgression partitions the genetic landscape of neuropsychiatric disorders and associated behavioral phenotypes).
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