Image: Milagros González
A bundle of recent genetic studies have suggested modern humans had sex with Neanderthals thousands of years ago when the two populations roamed the planet alongside each other. However, the bones left behind by the two species don't bear any obvious traces of interbreeding, and a new study of monkeys in Mexico shows why we shouldn't expect them to.
Researchers examined blood samples, hair samples and measurements collected from mantled howler monkeys and black howler monkeys that were live-captured and released in Mexico and Guatemala between 1998 and 2008. The two monkey species splintered off from a common ancestor about 3 million years ago; today they live in mostly separate habitats, except for a "hybrid zone" in the state of Tabasco in southeastern Mexico, where they coexist and interbreed.
Through an analysis of genetic markers, from both mitochondrial DNA (the DNA in the cells' energy-making structures that gets passed down by mothers) and nuclear DNA, the researchers identified 128 hybrid individuals that were likely the product of several generations of interbreeding. Even so, these hybrids shared most of their genome with either one of the two species and were physically indistinguishable from the pure individuals of that species, the team found.
"The implications of these results are that physical features are not always reliable for identifying individuals of hybrid ancestry," Liliana Cortés-Ortiz, an evolutionary biologist and primatologist at the University of Michigan, said in a statement. "Therefore, it is possible that hybridization has been underestimated in the human fossil record."
The work on howler monkeys was part of the doctoral dissertation of Mary Kelaita, now a postdoctoral fellow at the University of Texas at San Antonio. Kelaita added that the study "suggests that the lack of strong evidence for hybridization in the fossil record does not negate the role it could have played in shaping early human lineage diversity."
When scientists finally finished sequencing the Neanderthal genome in 2010, they revealed that between 1 percent and 4 percent of some modern humans' DNA came from the stocky hominids. This suggested humans had sex with Neanderthals, picking up some genes, and possibly even an immunity boost, from Neanderthals before the population disappeared about 30,000 years ago. But not all scientists are convinced the genetic evidence alone proves ancient interbreeding and a study last year found that even if humans and Neanderthals did have sex, those encounters would have rarely produced offspring.
The scientists of the new study say more work is needed to learn about interbreeding and the factors governing the expression of physical characteristics in hybrid individuals.
The research was detailed online Friday (Dec. 7) in the American Journal of Physical Anthropology.
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14 Comments
Add CommentI still haven't found any record of Neanderthal mitochondrial DNA in present day human populations from the info available on the Net.
Reply | Report Abuse | Link to thisIf Neanderthal mDNA still persisted it would be evidence of amiable interbreeding between Neanderthals and 'Moderns' as professed by some scientists in documentaries. If no living Neanderthal mDNA is ever found still alive in humans that would be more of an indication of forced copulations on Modern females by Neanderthal males. Such forced copulations are a common facet of warfare as a means of human reproduction (Michael Ghiglieri, The Dark Side Of Man) even in those contemporary African populations who do not have any Neanderthal ancestry.
The increased physical strength that interbred males would have inherited from Neanderthal fathers would have been an edge in surviving the very common phenomenon of human intra-sexual aggression. Greater physical strength would have also benefited humans in all other sorts of activities.
But we won the war, therefore it is likely we won most of the battles. So it is far more likely that Europeans and Asians who carry these markers received them through Neanderthal females who were captured by modern humans. Remember slavery as well as forcible adoption occurs in nature all up and down the evolutionary scale, look at ants.
Reply | Report Abuse | Link to thisOk, they may or may not have successful interbred, but if they lived in the same place at the same time... they hooked up. No doubt. Human/Neanderthal sex is as likely as human/barnyard animal sex, which of course is horrifying, gross and disgusting, and happening right now somewhere in this great nation.
Reply | Report Abuse | Link to thisIt's always interesting to me that great physical strength is given such high regard as it relates to survival. I think there are equal if not more examples of efficient stature being much more sustainable over long periods of time, while great strength requires great fuel, and is generally only effective in the decision-making and survival process of ancient peoples at arms length or less.
Reply | Report Abuse | Link to thisDespite all caveman movies you've ever seen, man's greatest survival skill has most often been his ability to visualize events that have not yet happened, a skill possibly unique to man. Perky pectorals? Not so much.
DrDawg, Oh definitely if size and strength were the deciding factors, then woolly mammoths or even Dinos. Would rule the world. And hey lets face it, if there were wildly different hominids around we would be chasing the poor dears all around the landscape, because they're exotic". And the inbred attraction to the exotic helps to prevent inbreeding.
Reply | Report Abuse | Link to thisIf a percentage of our DNA stems from Neanderthals, how could it have got there without interbreeding?
Reply | Report Abuse | Link to this"But not all scientists are convinced the genetic evidence alone proves ancient interbreeding and a study last year found that even if humans and Neanderthals did have sex, those encounters would have rarely produced offspring."
Reply | Report Abuse | Link to thisReading the linked "LiveScience" article, which also provides no reference links, some research is described as having determined that interbreeding would not likely have produced offspring from a simulation model of species interactions! Sorry, but I'll consider the genetic evidence to be more substantial than someone's presumptions about species interactions sanctified by a 'scientific' simulation model.
IMO this article is more subscription junk content. The advertisements cluttering up LiveScience articles are so gross I prefer not to read them, especially since they do not contain any links to scientific research material or even any reference information.
Fred Astaire and Ginger Rodgers where are you when we need you?
Reply | Report Abuse | Link to thisInteresting that one would characterize Neanderthals as not-human and interbreeding as "disgusting" and "barnyard". I was reminded on similar visceral reaction in recent history to inter-racial pairings. I would think that a member of either species sixty thousand years ago would fall seriously short of modern erotic standard, if for no other reason of personal grooming and dental hygene. I would recomment Isaac Asimov's The Ugly Little Boy for perspective.
Reply | Report Abuse | Link to thisProbably right in your backyard!
Reply | Report Abuse | Link to thisI would like to remind everyone that our entire knowledge of neanderthals DNA and physical attributes comes from a collection of bones that would not even fill a pickup truck's bed. And from that evidence average neanderthal brain's were significantly larger than modern humans brains.
Reply | Report Abuse | Link to this"If no living Neanderthal mDNA is ever found still alive in humans that would be more of an indication of forced copulations on Modern females by Neanderthal males."
Reply | Report Abuse | Link to thisNeanderthal men raping human women is not the only explanation. It is also possible that copulations between a human male and a neanderthal female resulted in infertile offspring, just as with mating between lions and tigers.
I got my DNA test at 23andme and it says I am 3.1% Neanderthal, which is in the 98% percentile. I am curious about human/neanderthal interbreeding and blood type. Has anyone seen any research on that? Like what blood type were most neanderthals, and did interbreeding with them cause new blood types, like O negative, etc...
Reply | Report Abuse | Link to thisAlso, If the neanderthal human sex was rape and not consensual sex, then I think the more likely scenario would have been human men raping neanderthal women, and not neanderthal men raping human women.
I know I'm missing something obvious but why is our DNA 90-99%* similar to chimps', but only 2-7%* of Neanderthals'?
Reply | Report Abuse | Link to this(* depending on source and % of genome compared.)