New Study Suggests Interbreeding with Neanderthals Led to Increase in Risk of Diabetes
Now that the both the human (H. sapiens) and the Neanderthal (H. neanderthalensis) genomes have been mapped and fully documented, any research into genetic variation in modern human populations permits scientists to trace the origins of gene types back into the history of hominin evolution. A large scale study of people living in Latin America has revealed that their increased risk of diabetes could have been inherited as a result of modern humans interbreeding with a Neanderthal population.
In a paper published in the academic journal “Nature”, scientists from Harvard Medical School (Massachusetts, United States), working in collaboration with the Max Planck Institute for Evolutionary Anthropology (Leipzig, Germany) and the Broad Institute (Massachusetts), carried out a large genome-wide association study (GWAS) on a sample of more than 8,000 Mexicans and other people from the Latin American population. The research mapped the genomes of the study sample and sought patterns within the genes in a bid to identify different traits and characteristics.
The team found that a variant on the genetic make up of the population, a gene form named SLC16A11 which when present in a genome, predicates those in the population to a higher likelihood of getting diabetes. This gene form has also been identified in a study of genetic material extracted from Neanderthal bones found in a cave located in the Altai Mountains, Siberia (Denisova cave). It can therefore be speculated that since the Denisova remains pre-date the evolution of modern man, this genetic trait which makes part of the population prone to type 2 diabetes may have been inherited as a result of interbreeding between ancient Homo sapiens and Neanderthals.
Could Neanderthals Have Passed On To Us the Gene Responsible for a Higher Risk of Diabetes?
Previous studies have shown that non-African modern humans carry a portion of Neanderthal (and Denisovan) genetic material in their genes. The proportion of Neanderthal is usually less than 2% but can be approaching 4% in some groups of Europeans. It had been thought that inherited genes from another member of the human family tree were present as H. sapiens shared a common ancestor with H. neanderthalensis, the common ancestor is believed to be Homo heidelbergensis, but the percentages were just too high for this fact to explain it all. The higher than expected levels of inherited genetic material in modern populations could only be explained by interbreeding between the two closely related species sometime in our recent past. It is likely that interbreeding between populations took place whenever these species came into close proximity and can perhaps be linked to movements of ice sheets and inter-glacial periods permitting migrations and the geographical spread of hominins.
It is known that people who carry the higher risk version of the gene are twenty-five percent more likely to have diabetes than those who do not have this gene type. Modern humans who have inherited copies of this gene from both parents are fifty percent more likely to have diabetes as a result. This higher risk gene (SLC16A11) has been found in nearly half of people with recent Native American ancestry, including the Latin American population. This study into the gene pool of Mexicans and other members of the population with a Latin American ancestry has shown that this population is at particular risk of diabetes. The higher risk gene, SLC16A11 is rarely found in genetic studies of European and African populations.
Co-author of the study, Jose Florez (Associate Professor of Medicine at Harvard Medical School) stated:
“To date, genetic studies have largely used samples from people of European or Asian ancestry, which makes it possible to miss culprit genes that are altered at different frequencies in other populations. By expanding our research to include samples from Mexico and Latin America, we’ve found one of the strongest genetic risk factors discovered to date, which could illuminate new pathways to target with drugs and a deeper understanding of the disease [diabetes].”
Scientists have been able to use knowledge of the genome of some species of hominins to map the routes of genetic inheritance. The routes and pathways are proving to be more complicated than previously thought due to the interbreeding that seems to have taken place between species. The functional implications of such inherited genetic material is only just beginning to be understood by researchers and geneticists.
Co-author of the study, David Altshuler (Broad Institute), commented:
“One of the most exciting aspects of this work is that we have uncovered a new clue about the biology of diabetes.”
The higher risk gene (SLC16A11) is part of a group of genes that code proteins for the transport of metabolites around the body. These metabolites are involved with the human body’s various chemical reactions. A spokesperson from Everything Dinosaur speculated that the gene could have evolved as a result in changes to our ancient ancestors diet. Changing the levels of SLC16A11 can change the amount of a type of fat that has been implicated in the risk of diabetes. This new study indicates that SLC16A11 could be involved in the transport of an unknown metabolite that impacts on the fat levels in cells and therefore increases the risk of type 2 diabetes.
It is very likely, that more insights into the origins of our genetic make up and the genetic variation seen in human populations will be revealed in the next few years as more ancient hominin fossil material is analysed for the presence of genetic data.