The interbreeding of Humans and Neanderthals occurred 47,000 years ago

The chronology of modern human-Neanderthal interbreeding has been refined by new research, which indicates that it started approximately 50,500 years ago and lasted for about 7,000 years. Beneficial features like skin pigmentation and immune resilience were contributed by this gene flow, which left non-African populations with 1-2 percent Neanderthal ancestry.

Neanderthal deserts, or areas of human genomes lacking Neanderthal genes, were also discovered by the study. These are probably the result of deadly gene variants. Understanding human adaptation, migration, and the genetic heritage of Neanderthals and other ancient hominins is enhanced by these discoveries.

Key Facts.

Timeline: Beginning 50,500 years ago, modern humans and Neanderthals interbred for roughly 7,000 years.

Impact on Genetics: Neanderthal genes improved skin pigmentation, immunity, and climate stress tolerance.

Genome Deserts: Regions devoid of Neanderthal genes quickly developed, indicating fatal gene incompatibilities.

UC Berkeley was the source.

The time period during which Neanderthals interbred with modern humans, beginning approximately 50,500 years ago and lasting approximately 7,000 years — until Neanderthals started to disappear — has been more precisely determined than ever before thanks to a new analysis of DNA from ancient modern humans (Homo sapiens) in Europe and Asia.

Because of this interbreeding, Eurasians now possess a large number of genes from our Neanderthal ancestors, which together account for between 1% and 2% of our genomes.

The genome-based estimate agrees with archeological evidence that Neanderthals and modern humans coexisted in Eurasia for 6,000–7,000 years.

The average date for Neanderthal-Homo sapiens interbreeding was determined to be approximately 47,000 years ago by the analysis, which included 58 ancient genomes that were sequenced from DNA found in contemporary human bones from all over Eurasia. The period of interbreeding has been estimated to have occurred between 54,000 and 41,000 years ago.

The new dates also suggest that by 43,500 years ago, the first migration of modern humans from Africa into Eurasia was essentially complete.

Priya Moorjani, an assistant professor of molecular and cell biology at the University of California, Berkeley, and one of the study’s two senior authors, stated, “The timing is really important because it has direct implications on our understanding of the timing of the out-of-Africa migration as most non-Africans today inherit 1-2 percent ancestry from Neanderthals.”.

It also affects our understanding of how people settled outside of Africa, which is usually accomplished by examining fossils or archeological artifacts from other parts of the world. “”.

Benjamin Peter from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig, Germany, and the University of Rochester in New York, who is also leading the genome analysis, will publish the findings in December. 13th edition of the journal Science in print.

Manjusha Chintalapati, a former UC Berkeley postdoctoral fellow currently employed at the company Ancestry DNA, and Leonardo Iasi, a graduate student at MPI-EVA, are the two lead authors.

East Asians have roughly 20% more Neanderthal genes than Europeans and West Asians, for instance, which may be explained by the longer duration of gene flow. Archaeological sites indicate that modern humans moved eastward approximately 47,000 years ago, which would have resulted in the intermixing of Neanderthal genes.

We demonstrate how complicated the mixing process was and how long it might have taken. Certain groups might have continued to mix for a longer amount of time, while other groups might have split apart over the 6,000–7,000 year period, according to Peter.

However, the data best fits a single shared gene flow period. “.”.

One of the primary discoveries is the accurate estimation of Neanderthal admixture timing, which was previously determined using individual ancient samples or in living people. Chintalapati stated that no one had attempted to model every ancient sample collectively. This made it possible for us to create a more comprehensive historical picture.

The genome contains Neanderthal deserts.

In 2016, Moorjani developed a technique that uses the frequently unfinished genomes of ancient people to infer the timing of Neanderthal gene flow. Only five ancient Homo sapiens genomes were accessible at the time.

In order to provide a more accurate date of 47,000 years ago, Iasi, Chintalapati, and their colleagues used this technique in their new study. They used the genomes of 275 modern humans worldwide and 58 previously sequenced genomes of ancient Homo sapiens who lived in Europe, Western, and Central Asia over the previous 45,000 years.

They attempted more intricate models created by Iasi and Peter to prove that the interbreeding was continuous over roughly 7,000 years rather than sporadic, instead of presuming the gene flow happened in a single generation.

MPI-EVA researchers conducted another independent study that will be published in December and confirmed the timing of the interbreeding between Neanderthals and modern humans. 12 in Nature, the journal.

There was also a date of 47,000 years ago in that study, which analyzed two recently sequenced genomes of Homo sapiens that lived approximately 45,000 years ago.

Despite being published in earlier research, the ancient genomes had not been examined to examine Neanderthal ancestry in such detail. We compiled a list of the segments of modern humans’ Neanderthal ancestry.

After examining all of these samples collectively, we concluded that the gene flow period was approximately 7,000 years, Chintalapati stated. In fact, the Max Planck group was able to directly date the Neanderthal gene flow by sequencing new ancient DNA samples. And they developed a timing that was comparable to ours. “.”.

The UC Berkeley/MPI-EVA team also examined certain parts of the modern human genome that are completely devoid of Neanderthal genes and other parts that contain Neanderthal genes.

When the two groups interbred, they discovered that regions devoid of Neanderthal genes—known as archaic or Neanderthal deserts—formed rapidly. This suggests that some Neanderthal gene variants in those regions of the genome must have been fatal to modern humans.

Oase cave in Romania, Ust’-Ishim in Russia, Zlatý kůň in the Czech Republic, Tianyuan in China, and Bacho Kiro in Bulgaria are examples of early modern human samples that predate 40,000 years. These samples already had these deserts in their genomes.

“We discover that 40,000-year-old very early modern humans have no ancestry in the deserts, so these deserts may have formed very quickly after the gene flow,” Iasi said.

Additionally, by examining the evolution of Neanderthal ancestry frequency over time and throughout the genome, we discovered high-frequency regions that may contain advantageous Neanderthal-introgressed variants. “”.

Previous studies have reported that the majority of high-frequency Neanderthal genes are associated with metabolism, skin pigmentation, and immune function. One Neanderthal immune gene variant, for instance, offers protection against the coronavirus that causes COVID-19.

In fact, over time, the frequency of some Neanderthal genes related to skin pigmentation and the immune system rose in modern humans, suggesting that they might have been beneficial to human survival.

“Neanderthals lived outside of Africa in harsh, Ice Age climates and were acclimated to the pathogens and climate of these regions.”. Some people who interbred with Neanderthals after modern humans left Africa presumably inherited Neanderthal genes that helped them adapt and survive in their new environment, according to Iasi.

“The discovery of some of these regions in samples that are 30,000 years old indicates that some of these regions were adapted right after the introgression,” Chintalapati continued.

Some genes, like the coronavirus resistance gene, might not have been helpful right away but eventually came in handy.

“Some genes become advantageous when the environment changes,” Peter stated.

Currently, Moorjani is examining Neanderthal sequences in East Asian individuals, who include genes from another early hominin group, the Denisovans, up to 0.1 percent of their genome in addition to a higher proportion of Neanderthal genes.

“Looking back at how variations passed down from our evolutionary cousins, Neanderthals and Denisovans, evolved over time is really cool,” Moorjani said.

We can now comprehend the dynamics of the mix of Neanderthals and contemporary humans thanks to this. “”.

Funding Alba Bossoms Mesa and Mateja Hajdinjak of MPI-EVA, as well as postdoctoral fellow Laurits Skov of UC Berkeley, were also co-authors of the Science article. The Burroughs Wellcome Fund and the National Institutes of Health provided funding for Moorjani’s study (R35GM142978).

Regarding this news about neuroscience and evolution.

Author: Sanders, Robert.

Berkeley University is the source.

Contact: UC Berkeley’s Robert Sanders.

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Initial Study: Restricted access.

“Neandertal ancestry through time: Insights from ancient and modern human genomes” by Priya Moorjani and colleagues. research.

abstract.

Ancient and modern human genomes provide insights into Neandertal ancestry over time.

INTRODUCTION.

Modern humans’ genetic and phenotypic variation is shaped by Neanderthal gene flow. The majority of non-Africans in the modern world have between 1% and 2% Neanderthal ancestry.

“Candidates of adaptive introgression” are genomic regions that have a high frequency of Neanderthal variants throughout the genome, while “deserts” are genomic regions that have no Neanderthal ancestry. “”.

The chronology and evolutionary mechanisms that have influenced the Neanderthal ancestry landscape, such as natural selection or genetic drift, are still unknown. Since it is difficult to distinguish between the effects of past demography and selection, the majority of earlier research has concentrated on the genomes of living people.

Through the direct observation of historical patterns of genetic variation, ancient DNA analyses have revolutionized the study of human evolutionary history.

PURPOSE.

In this study, we examined the evolutionary history of Neanderthal ancestry across time by analyzing genomic data from 275 diverse modern individuals and 59 ancient individuals sampled between 45,000 and 2200 years ago.

What is the functional legacy of Neanderthal ancestry in modern humans? (i) How is Neanderthal ancestry shared among individuals, by geography and time? (ii) When did Neanderthal gene flow occur and for how long did it last? (iii) How frequently do Neanderthal ancestry segments occur and where do they occur?

OUTCOMES.

The bulk of Neanderthal ancestry segments are shared across populations, and the sharing of Neanderthal ancestry segments reflects the population structure among non-Africans, according to a catalog of Neanderthal ancestry in ancient and modern humans.

The gene flow may have come from one or more closely related Neanderthal groups, based on the comparison with sequenced Neanderthals, such as Vindija, Altai, and Chagyrskaya. Oase, Ust’-Ishim, Zlatý kůň, and Bacho Kiro, the earliest modern humans, on the other hand, have a clear matching profile to the sequenced Neanderthals and a significant amount of unique Neanderthal ancestry. This suggests that some of the Neanderthal ancestry in these early individuals is not shared with modern humans after 40,000 years.

Through an analysis of the lengths and distributions of Neanderthal ancestry segments in ancient individuals, we discovered evidence of a single, prolonged Neanderthal gene flow that lasted for approximately 7000 years, beginning about 47,000 years ago. This is in line with archeological evidence suggesting that early modern humans and Neanderthals may have overlapped in Europe.

Lastly, we looked at the frequency of Neanderthal ancestry over time and across the genome. In addition to areas that were instantly adaptive for contemporary humans, we also found new candidates for adaptive introgression, some of which developed adaptiveness more recently due to introgressed standing variation.

The majority of Neanderthal deserts, which were present in the earliest modern human genomes, were formed quickly following the gene flow on the autosomes and the X chromosome. The X chromosome notably shows a nonuniform and nonrandom distribution of Neanderthal ancestry, with sizable Neanderthal ancestry deserts overlapping evidence of sweeps in non-Africans that has been previously identified.

CONCLUSION.

The complicated history of Neanderthal gene flow into modern humans is clarified by our research. There is substantial evidence that Neanderthal genes flowed into the common ancestors of all non-Africans between 50,500 and 43,500 years ago. These dates offer a lower bound on when people left Africa and settled in non-African regions.

Rapidly following the gene flow, the majority of natural selection—both positive and negative—on Neanderthal ancestry left distinct marks on the genetic diversity of the first modern humans outside of Africa.