2023-10-18 20:00:10
Around 50,000 to 70,000 years ago, modern man carried out his main wave of expansion out of Africa, this is the theory called Out of Africa. Upon arriving in Europe, in this region they encountered the Neanderthals, who had been living in the western part of the Eurasian continent for hundreds of thousands of years. This crossing led to them reproducing with the hunter-gatherer human societiesbut finally the A wise man prevailed and the Neanderthals became extinct.
However, this disappearance was not sudden and, at coexist for millennia In both species, Neanderthal DNA was integrated into the genome of the sapiens.
Eurasians have about 2% DNA of Neanderthal origin. In the genomes of Asians this percentage is between 8% and 24% higher
As a consequence, there is currently a presence of approximately 2% of DNA of Neanderthal origin in the Eurasian population. However, this percentage varies slightly depending on the region, as it is somewhat more abundant in the genomes of Asian populations than in European populations (they have around 8% to 24% more).
To understand this common history between the two species, research led by the University of Geneva (UNIGE) has studied the distribution of the portion of DNA inherited from Neanderthals in the genomes of modern humans, over the last 40,000 years.
To this end, they used a data base provided by Harvard Medical School that includes more than 4,000 genomes from individuals who have lived in Eurasia in that period. These statistical analyzes revealed subtle variations in time and geographic space.
By analyzing paleogenomes of modern men up to the present, we observe that there is a part of Neanderthal DNA that increases as distance from the source of expansion ‘Out of Africa’
Claudio Quilodran, researcher at UNIGE
“By analyzing paleogenomes of modern men up to the present, we observed that there is a part of Neanderthal DNA that increases as distance from the source of expansion Out of Africa.
However, this expansion does not explain the relatively greater Neanderthal ancestry observed today in eastern Asia, compared to western Europe. It is a second expansion, that of the first farmers coming from the Middle East (Anatolia), who were closer to the original expansion and, therefore, had relatively less Neanderthal DNA, which decreased the levels of this ancestry in Europe,” he tells SINC. Claudio Quilodran, from UNIGE and main co-author of the research. The work is published in the magazine Science Advances.
During the transition to the Neolithic, that is, with the transition from the hunter-gatherer lifestyle to the agricultural style coming from the inhabitants of Anatolia (western peninsula of Turkey) and the Aegean area between 10,000 and 5,000 years ago, this is what leads to a decrease in the proportion of DNA of Neanderthal origin in the genomes of European populations.
These first farmers They carried a lower proportion of DNA of Neanderthal origin than the inhabitants of Europe at the same time. By mixing, the genomes of Anatolian farmers ‘diluted’ the Neanderthal DNA a little more.
How to explain the differences between Europe and Asia
One hypothesis to explain this is that natural selection would not have had the same effect on genes of Neanderthal origin in Asian and European populations. But at UNIGE they are working on another hypothesis based on computer simulations that suggests that such differences could be explained by the migratory flows: when a migrant population hybridizes with a local population, in their cohabitation area, the DNA ratio of the local population tends to increase with distance from the point of departure of the migrant population, in this case Africa, point of origin of the A wise man.
“Precisely, the interesting thing about our study is that We propose this new hypothesis [flujos migratorios]to understand these small differences that we observe today. This is explained because the individuals who live on the edge of the wave of demographic expansion are less numerous than in the center of the expansion, which means that they have a greater probability of increasing Neanderthal DNA, by reproducing with them or randomly, since the population is small,” explains Quilodran.
The interesting thing about our study is that we propose this new hypothesis of migratory flows to understand the small differences that we observe today
Claudio Quilodran
The results of the research indicate that in the period after the dispersion of the A wise man From Africa, the genomes of Paleolithic hunter-gatherers living in Europe contained a slightly higher proportion of DNA of Neanderthal origin, compared to the genomes of those living in Asia.
This result is contrary to the current situation, but agrees with paleontological data, since the presence of Neanderthals was recorded mainly in Eurasia occidental —No Neanderthal bones have been discovered further east than in the Altai region of Siberia.
“We are beginning to have enough data to describe with increasing precision the percentage of DNA of Neanderthal origin in the genome of sapiens in certain periods of prehistory. Therefore, our work can serve as a reference so that future studies can more easily detect genetic profiles that deviate from the mean and that, therefore, could reveal an advantageous or disadvantageous effect”, concludes Mathias runslast author of the study.
Reference:
Claudio S. Quilodrán et al. “Past human expansions shaped the spatial pattern of Neanderthal ancestry”. Science Advances.
Rights: Creative Commons.
#arrival #Middle #Eastern #farmers #Europe #diluted #Neanderthal #DNA