An article published in the journal “Nature Communications” reports the results of the study of the inner ear of Neanderthals that suggests that at a certain point in their history there was a genetic bottleneck that may have contributed to their extinction. A team of researchers examined the semicircular canals, structures whose development is strongly determined by genes, to assess the history of Neanderthals. According to the conclusions, the morphological diversity of these anatomical structures shows a decline about 110,000 years ago.
The image (Courtesy Alessandro Urcioli. All rights reserved) shows the areas where the fossils object of the study on the inner ear were found with the one called Almud 1 enlarged and a reconstruction of the inner ear’s semicircular canals.
This is not the only recent research that suggests a genetic stagnation of Neanderthals because a few weeks ago, an article was published in the journal “Scientific Reports” that focuses on the blood groups of Homo sapiens, Denisovans, and Neanderthals. Genetic analysis shows that Neanderthals had a blood type that’s very rare in Homo sapiens with very limited variability over about 80,000 years. This may have made them vulnerable to various health problems.
The strong genetic component in the shape of the semicircular canals of the inner ear allows studying the genetic variability of a population indirectly. In this way, a group of researchers took advantage of the availability of many Neanderthal fossils found in different sites dating back to different eras. In the case of the fossils from the Atapuerca / Sima de los Huesos site, in today’s Spain, they considered the fossils as pre-Neanderthal.
The fossils attributed to Neanderthals are those from Krapina, in today’s Croatia, and the so-called La Ferrassie 1, discovered in today’s France. Homo sapiens fossils from similar eras were examined to compare the variability of the semicircular canals with those of Neanderthals.
The result is that around 110,000 years ago there was a decline in the anatomical variability of Neanderthals compared to that existing in Homo sapiens. This is a result consistent with the genetic knowledge of Neanderthals, possible thanks to the fact that DNA was recovered from well-preserved bones. Precisely this availability allowed to conduct a study on the blood groups of Neanderthals that offers further confirmation of a possible genetic bottleneck in the last phase of the history of this species of hominins.
The authors of this research discovered that Neanderthals had a blood group that is very rare among modern humans. At the same time that Homo sapiens were adding variability from this point of view, Neanderthals showed stagnation in the last 80,000 years of their history. This could indicate a decline in their population with problems of interbreeding within small groups. The Neanderthal blood group may have also created problems in crossbreeding with Homo sapiens populations due to an incompatibility between the blood groups of the parents.
The possible problem of inbreeding among Neanderthals was also addressed in an article published in the journal “PLOS ONE” in November 2019. At this point, various approaches in research are suggesting that Neanderthals started suffering from genetic problems that may have made them more vulnerable.
The enigma of the extinction of Neanderthals remains open. Comparative studies with Homo sapiens show a genetic diversification at the same time in which the decline of Neanderthals may have begun, and this may have contributed to the success of one species at the expense of the other. All this keeping in mind that there were crossbreedings between the two species and among modern European populations it’s normal to have Neanderthal genes.
