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At several spot in our tangled history , modern humans mated withNeanderthals .
This has left a revealing signature in the genome of modern humans today , and this Neanderthal DNA impacts our health in infinite ways .
Neanderthal DNA may have been lost in modern humans following interbreeding events, because it was incompatible with our own DNA, scientists say.
However , there ’s one part of our genome that miss any Neanderthalian deoxyribonucleic acid : the Y chromosome . But why ?
Experts tell Live Science that some of that could be fortune . But it ’s also possible that genes from Neanderthal male person were incompatible with the femaleHomo sapienscarrying them . That would mean only distaff hybrids were capable to procreate .
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Neanderthal DNA is not found on the Y chromosome in modern men, and scientists don’t fully understand why.
The vanishing “Y”
The Y chromosome is one of two types ofsex chromosomesin humans . Females carry two transcript of the X chromosome , while males have a bun in the oven one X and one yttrium chromosome . The Y chromosome can only be passedfrom father to son .
At first , scientists had been analyzing DNA taken from the fossilized clay of distaff Neanderthals . However , in 2016 , a report publish in theAmerican Journal of Geneticsexamined a Neanderthal Y chromosome from a 49,000 - year - former male person from Spain .
" We ’ve never observed the Neanderthal yttrium chromosome DNA in any human sample ever tested,“Carlos Bustamante , co - aged study author and a universe geneticist at Stanford University , said in astatementat the sentence .
Harmful mutations that impact a population’s evolutionary fitness are more likely to accumulate within a smaller population than a larger one.
So why might this neandertal DNA have seemingly vanished without a vestige ?
The simplest answer may be that it was arbitrarily lost from the human factor consortium over thousands of years .
" The amount of oafish DNA in modernistic humans today is relatively humble so it could have been misplace by drift,“Fernando Mendez , lead study author , who at the time was a postdoctoral researcher at Stanford , told ABC News . In other Logos , it ’s not that Neanderthal DNA was less " fit " than forward-looking human DNA from an evolutionary linear perspective but rather that it was justlost over time .
Another possibility is that the Neanderthal Y chromosome was inappropriate with our own deoxyribonucleic acid . For instance , the squad find out that three of the Neanderthal genes on the Y chromosome that dissent from those find in humans function as part of theimmune system . These genesallow the resistant system to differentiate friend — akathe eubstance ’s own cells — from foe . Failure to properly distinguish " self " from " encroacher " is why tissue transplants from Man to womencan be rejectedor why a mother ’s resistant system of rules may aggress a male fetusduring pregnancy , causing stillbirth .
Related:‘Simply did not work ' : Mating between Neanderthals and modern humans may have been a product of failed alignment , says archaeologist Ludovic Slimak
It ’s therefore conceivable that the resistant systems of mod women consistently assail male babies who carried Neanderthal desoxyribonucleic acid on their yttrium chromosome , lead to recurrent miscarriages and eventually the personnel casualty of Neanderthal Y factor .
If modern char who interbred with Neanderthals had few boys than other couple , then systematically the boys that live are potential to have fewer boys , Mendeztold ABC News . This hypothesis aligns with an old theory called " Haldane ’s formula , " which propose that if breeding between genetically - dissimilar population lead to sterility , it is likely to be in the sexual practice — in this case male — that carries two unlike sex chromosome .
Far-reaching loss
This is n’t the first time in our evolutionary story that the Neanderthal Y chromosome go to compete with its modernistic human twin .
Between 550,000 and765,000 geezerhood ago , the population that would give rise toHomo sapiensdiverged from Neanderthals and another group of now extinct human relative calledDenisovans .
However , a subject area published in the journalSciencein 2020 revealed that sometime between 370,000 and 100,000 year ago , Neanderthals and other modern humans interbreed . By 100,000 years ago , the Neanderthal Y was totally replaced by the one fromHomo sapiens .
Scientists do n’t know why this chance , Martin Petr , a co - senior report source and research worker and programmer at the University of Copenhagen in Denmark , told Live Science .
But a likely account , Petr hypothesized , is that for hundred of chiliad of years , Neanderthals had a very humble universe size equate with early modern humans . Low population sizes allow harmful mutations to accumulate within the factor pocket billiards at a high charge per unit than within a larger population , he say .
If you then introduce " healthier " former forward-looking human DNA into the mix , natural excerpt would favor this modern human DNA , which would have then sweep through the neandertal universe .
However , without a lot more genomic data point from Neanderthals that would admit scientist to study the functional impact of inheriting this former modern human DNA , this is only a hypothesis , Petr said .
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Many unknowns
Unfortunately , it ’s still too early to definitively say why Neanderthal Y DNA was lose in both these example , Adam Siepel , a computational life scientist at Cold Spring Harbor Laboratory in New York , told Live Science in an email .
It ’s still possible the replacement occurred due to random genetical drift , he added .
' More neandertal than human ' : How your wellness may depend on DNA from our long - lose ancestors
learn more :
— 10 unexpected ways Neanderthal DNA affects our wellness
— Could Neanderthals talk ?
— What ’s the difference between Neanderthals and Homo sapiens ?
broadly speaking - speaking , the deprivation of a Y chromosome line due to interbreeding is not a uncommon phenomenon , Carles Lalueza - Fox , carbon monoxide - author of the 2020 Science study and a paleogenomics research worker at the Institut de Biologia Evolutiva in Spain , told Live Science in an email .
This is because the Y chromosome is only inherited paternally , he said . This is opposed to other chromosome in the body that are passed on to the next generation by both parent . This means that the Y chromosome is more prostrate to being " misplace " over prison term , he say .
Ever marvel whysome citizenry build brawn more well than othersorwhy freckles come out in the sun ? Send us your questions about how the human dead body works tocommunity@livescience.comwith the subject line " Health Desk Q , " and you may see your question answer on the internet site !
