\n<\/p>\n
Tens of thousands of years ago, as modern humans migrated into northerly territories inhabited by our ancient cousins, the Neanderthals, the two species met \u2013 and sometimes mated.<\/p>\n
Now, genetic evidence has revealed a striking imbalance in these prehistoric trysts, suggesting that interbreeding was mostly between male Neanderthals and female humans.<\/p>\n
This ancient mating pattern, they have concluded, explains why Neanderthal DNA is largely missing from the human X chromosome.<\/p>\n
\u201cWe found a pattern indicating a sex bias: gene flow occurred predominantly between Neanderthal males and anatomically modern human females,\u201d said Dr Alexander Platt, a senior research scientist at the University of Pennsylvania and first author of the research.<\/p>\n
The ancestors of modern humans and the closest related species, the Neanderthals, diverged, forming two distinct groups, about 600,000 years ago.<\/p>\n
\u201cOur ancestors evolved in Africa, while the ancestors of Neanderthals evolved in and adapted to life in Eurasia,\u201d said Sarah Tishkoff, the David and Lyn Silfen University professor in genetics and biology at the University of Pennsylvania, who led the research. \u201cBut that separation was far from permanent.\u201d<\/p>\n
Over hundreds of millennia, human populations migrated into Neanderthal territories and back again, and when these groups met, they mated, swapping segments of DNA. Today, individuals of non-African heritage typically have a few per cent Neanderthal DNA, while those of African heritage typically have a lower proportion.<\/p>\n
\u201cIt\u2019s hard to say how many times these events occurred,\u201d said Tishkoff. \u201cBut I\u2019m just getting the sense that this was happening more than we originally speculated.\u201d<\/p>\n
However, Neanderthal DNA carried by modern humans is not evenly distributed across the genome. In particular, there are missing areas of Neanderthal DNA, known as \u201cNeanderthal deserts\u201d, along the X chromosome.<\/p>\n
Platt said: \u201cFor years, we just assumed these deserts existed because certain Neanderthal genes were biologically \u2018toxic\u2019 to humans \u2013 as tends to be the case when species diverge \u2013 so we thought the genes may have caused health problems and were likely purged by natural selection.\u201d<\/p>\n
However, the latest research, published in the journal Science, puts forward an alternative explanation.<\/p>\n
The researchers studied the presence of modern human DNA preserved in three Neanderthals \u2013 the Altai, Chagyrskaya and Vindija \u2013 and compared this dataset with genetic data from specific sub-Saharan African populations that lack Neanderthal ancestry.<\/p>\n
If the two species were biologically incompatible, modern human DNA should have been missing from Neanderthal X chromosomes as well. However, the analysis revealed that Neanderthal X chromosomes had a 62% excess of modern human DNA compared with their other chromosomes \u2013 a mirror-like reversal of the distribution of Neanderthal DNA in human populations.<\/p>\n
Because females carry two X chromosomes and males carry only one, mating direction matters. If Neanderthal males partnered more often with modern human females, fewer Neanderthal X chromosomes would enter the human gene pool, and more human X chromosomes would enter Neanderthal populations.<\/p>\n
\u201cMating preferences provided the simplest explanation,\u201d Platt said.<\/p>\n
The findings did not, Platt said, suggest that Neanderthal males were particularly attractive to modern human females or vice versa. \u201cIt could be that everybody considered the interspecies matings as gross \u2013 or attractive,\u201d he said. \u201cBut it seems that one direction was viewed as better, or less worse, than the other.\u201d<\/p>\n
The strength of the effect suggested that it also went beyond the first mating event and that males with Neanderthal heritage would be preferred over females with Neanderthal heritage, within a predominantly modern human population. \u201cIt\u2019s something that had to continue within a population after the first mating had already happened,\u201d Platt said.<\/p>\n","protected":false},"excerpt":{"rendered":"
Tens of thousands of years ago, as modern humans migrated into northerly territories inhabited by our ancient cousins, the Neanderthals, the two species met \u2013 and sometimes mated. Now, genetic evidence has revealed a striking imbalance in these prehistoric trysts, suggesting that interbreeding was mostly between male Neanderthals and female humans. This ancient mating pattern,<\/p>\n","protected":false},"author":1,"featured_media":45354,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[15935,14644,3698,14088,4453,3141,3415],"class_list":{"0":"post-45353","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-bias","9":"tag-direction","10":"tag-humans","11":"tag-mating","12":"tag-neanderthals","13":"tag-research","14":"tag-suggests"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/45353","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=45353"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/45353\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/45354"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=45353"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=45353"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=45353"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}