Summary: New study refines the timeframe of interbreeding between modern humans and Hominids, showing it began about 50, 500 years ago and lasted about 7, 000 times. This gene movement left non-African populations with 1-2 % Neanderthal ancestry, contributing valuable traits like defensive endurance and skin color.
Ancient deserts, regions in mortal genomes bereft of Neanderthal genes, are also said to be caused by devastating gene variants. These results deepen our understanding of human version, movement, and the genetic legacy from Hominids and other historical hominins.
Major Information
- Timeline: Humans and modern humans interbred for about 7, 000 times, starting 50, 500 times before.
- Biological Effect: Neanderthal genes boosted resistance, skin color, and adaptation to severe climates.
- Genome Deserts: Places lacking Ancient genes formed quickly, suggesting devastating gene incompatibilities.
Origin: UC Berkeley
A new study of DNA from old modern humans ( Homo sapiens ) in Europe and Asia has determined, more perfectly than ever, the time period during which Humans interbred with modern humans, starting about 50, 500 years before and lasting about 7, 000 times — until Neanderthals began to disappear.
Eurasians were left with a large number of genes that had been inherited from our Neanderthal ancestors, which currently account for between 1 % and 2 % of our genomes.
The genome-based measure is consistent with historical data that current humans and Neanderthals lived side-by-side in Eurasia for between 6, 000 and 7, 000 years.
The study, which involved present-day human dna as well as 58 old chromosomes sequenced from DNA found in modern human vertebrae from around Eurasia, found an average day for Neanderthal-Homo sapiens , intermarriage of about 47, 000 years ago. Prior estimates for the occasion of crossbreeding ranged from 54, 000 to 41, 000 centuries ago.
The new times also point out that 43, 500 years ago, the earliest human migration from Africa to Eurasia was essentially above.
” The schedule is really important because it has direct relevance on our understanding of the schedule of the out-of-Africa movement as most non-Africans immediately inherit 1-2 % heritage from Neanderthals”, said , Priya Moorjani, an assistant professor of molecular and cell biology at the University of California, Berkeley, and one of two top authors of the study.
It also has implications for determining whether countries outside of Africa have settled, which are generally determined by examining historical finds or fossils in various globe areas.
The genome analysis, also led by , Benjamin Peter , of the University of Rochester in New York and the Max Planck Institute for Evolutionary Anthropology ( MPI-EVA ) in Leipzig, Germany, will be published in the Dec. 13 print issue of the journal , Science.
The two cause scholars are  , Leonardo Iasi, a grad student at MPI-EVA, and Manjusha Chintalapati, a previous UC Berkeley postdoctoral fellow now at the firm Ancestry DNA.
The longer protein circulation may contribute to explaining, for instance, why East Asians have around 20 % more Neanderthal genes than West Asians and Europeans. According to historical evidence, if current people had moved east about 47, 000 years before, they would already have had intermixed Ancient genes.
We demonstrate that the mixing time was very lengthy and could have taken a while. According to Peter, there were several groups that could have broken up during the 6, 000 to 7, 000-year time, and some parties may have continued to mix for a longer period of time.
However, a single expressed phase of protein flow best fits the data.
One of the main results is the exact calculation of the Neanderthal admixture’s timing, which was recently estimated using only ancient samples or in contemporary people. Nobody had attempted to combine all of the old tests, according to Chintalapati. This made it possible to reconstruct a more accurate picture of the past.
Ancient desert in the dna
Moorjani developed a method that uses frequently inadequate genomes of old people to determine the timing of Ancient gene flow. At that time, just five archaic , Homo sapiens , genomes were attainable.
For the new research, Iasi, Chintalapati and their colleagues employed this method with 58 recently sequenced genomes of ancient , Homo sapiens , who lived in Europe, Western and Central Asia over the past 45, 000 years and the genomes of 275 global modern humans to provide a more precise day — 47, 000 years ago.
Instead of assuming that the gene flow occurred over a single generation, they instead tried more complex models created by Iasi and Peter to demonstrate that the interbreeding spanned an estimated 7, 000 years.
Another, independent study conducted by MPI-EVA researchers and scheduled to be published Dec. 12 in the journal , Nature, confirmed the timing of the interbreeding between Neanderthals and modern humans.
That study, an analysis of two newly sequenced genomes of , Homo sapiens , that lived about 45, 000 years ago, also found a date of 47, 000 years ago.
” Even though the ancient genomes were previously published, they had not been thoroughly examined when examining Neanderthal ancestry.” We created a list of modern humans ‘ Neanderthal ancestry segments.
By jointly analyzing all these samples together, we inferred the period of gene flow was around 7, 000 years”, Chintalapati said. The Max Planck team actually analyzed fresh ancient DNA samples to determine the Neanderthal gene flow. And they came up with a timing comparable to ours.
The UC Berkeley/MPI-EVA team also compared the Neanderthal gene-depletion regions of the modern human genome to those that do not include any Neanderthal genes completely.
According to them, areas that had no Neanderthal genes, such as archaic or Neanderthal deserts, developed quickly after the two groups interbred, leading to the hypothesis that some Neanderthal gene variants in those regions of the genome must have been lethal to contemporary humans.
Early modern human samples that are older than 40, 000 years — samples from Oase cave in Romania, Ust’-Ishim in Russia, Zlatý kůň in the Czech Republic, Tianyuan in China and Bacho Kiro in Bulgaria  , — already contained these deserts in their genomes.
” We discover that very early modern humans from 40, 000 years ago don’t have any ancestry in the deserts, so these deserts may have formed very quickly after the gene flow,” said Iasi.
We also examined the variations in Neanderthal ancestry over time and across the genome, and we discovered regions that are present at high frequencies, perhaps because they contain beneficial variants that were introduced from Neanderthals.
Most of the high-frequency Neanderthal genes are related to immune function, skin pigmentation and metabolism, as reported in some previous studies. One immune gene variant inherited from Neanderthals, for instance, has protective effects on coronavirus that causes COVID-19.
Some Neanderthal genes involved in the immune system and skin pigmentation have recently become more common, suggesting that they may have contributed to the survival of humans.
Neanderthals were residing in harsh, Ice Age climates outside of Africa and had adapted to the climate and the pathogens there. Some people inherited Neanderthal genes, which presumably enabled them to adapt and thrive better in the environment, when modern humans left Africa and interbred with Neanderthals, according to Iasi.
” The fact that some of these regions were actually adapted right away after the introgression shows that we found some of these regions already in 30, 000-year-old samples,” Chintalapati continued.
Other genes may not have been immediately useful but eventually gained in use, such as the gene that controls coronavirus resistance.
” The environment changes and then some genes become beneficial”, Peter said.
Neanderthal sequences in people of East Asian descent, who have somegenes from another early hominin group, the Denisovans, account for up to 0.1 % of their genome, according to Moorjani.
” It’s really cool that we can actually peer into the past and see how variants inherited from our evolutionary cousins, Neanderthals and Denisovans, changed over time”, Moorjani said.
This enables us to comprehend the dynamics of the Neanderthal-Muslim hybrid.
Funding: Other co-authors of the , Science , paper were postdoctoral fellow Laurits Skov of UC Berkeley and Alba Bossoms Mesa and Mateja Hajdinjak of MPI-EVA. The Burroughs Wellcome Fund and the National Institutes of Health ( R35GM142978 ) provided funding for Morjani’s research.
About this news about neuroscience and evolution
Author: Robert Sanders
Source: UC Berkeley
Contact: Robert Sanders – UC Berkeley
Image: The image is credited to Neuroscience News
Original Research: Closed access.
” Neandertal ancestry through time: Insights from genomes of ancient and present-day humans” by Priya Moorjani et al. Science
Abstract
Neandertal ancestry through time: Insights from genomes of ancient and present-day humans
INTRODUCTION
Genetic and phenotypic variation in contemporary humans have been influenced by Neanderthal gene flow. Most non-Africans living today derive ~1 to 2 % of their ancestry from Neanderthals.
Some genomic regions are labeled as “deserts,” while others are devoid of any Neanderthal ancestry and are referred to as “deserts” and have a high frequency of Neanderthal variants that are present in some genomic regions.
However, the timing and evolutionary processes, for example, genetic drift or natural selection, that have shaped the landscape of Neanderthal ancestry remain elusive. Most of the previous studies have focused on genomes of present-day individuals, where separating the effects of past demography and selection is challenging.
By enabling direct observation of historical genetic variation patterns, ancient DNA analyses have transformed research into human evolutionary history.
RATIONALE
In order to study the evolution of Neanderthal ancestry throughout time, we analyzed genomic data from 59 ancient individuals sampled between 45, 000 and 2200 years before the present and 275 diverse present-day individuals.
We examined the frequency, length, and distribution of Neanderthal ancestry segments over time to answer the following questions: ( i ) How is Neanderthal ancestry shared among individuals, by geography and time? ( ii ) When and how long did Neanderthal gene flow last? and ( iii ) What are the Neanderthal ancestry’s functional remains in contemporary people?
RESULTS
We created a list of Neanderthal ancestry in both ancient and contemporary people, and we discovered that the majority of the Neanderthal ancestry segments are distributed among populations and that the Neanderthal ancestry segments are shared among non-Africans.
The comparison with sequenced Neanderthals, for example, Vindija, Altai, and Chagyrskaya, suggests that the gene flow occurred from a single or multiple closely related Neanderthal groups. By contrast, the earliest modern humans—Oase, Ust’-Ishim, Zlatý kůň, and Bacho Kiro—possess substantial unique Neanderthal ancestry and a distinct matching profile to the sequenced Neanderthals, indicating that some Neanderthal ancestry in these early individuals is not shared with modern humans after 40, 000 years.
We discovered evidence for a single extended period of Neanderthal gene flow that spanned 47, 000 years ago and spanned 7000 years by studying the distribution and lengths of the Neanderthal ancestry segments in ancient people. This is in line with archaeological evidence that suggests there might have been a conflict between early modern people and Neanderthals in Europe.
Finally, we examined the evolution of Neanderthal ancestry over time and across the genome. We discovered new types of adaptive introgression, including regions that were initially adaptable for modern people and those that have evolved more recently as a result of introgressed standing variation.
Most Neanderthal deserts, which were found on the autosomes and the X chromosome, developed quickly following the flow of the gene, and they were also found in the earliest modern human genomes. Notably, the X chromosome exhibits a non-uniform and nonrandom Neanderthal ancestry, with significant Neanderthal deserts overlapping previously undiscovered sweep patterns in non-Africans.
CONCLUSION
Our study provides insights into the intricate history of the Neanderthal gene flow into contemporary people. We found strong support for a single, extended period of Neanderthal gene flow into all non-Africans ‘ common ancestors that took place between 50, 500, and 43, 500 years ago. These times provide a lower estimate of the frequency of the migration and settlement of areas outside of Africa.
The majority of natural selection on Neanderthal ancestry, both positive and negative, took place very quickly after the gene flow, which gave clear indications about the genetic diversity of the earliest modern people outside of Africa.