Study casts doubt on human-Neanderthal interbreeding theory

Cambridge scientists claim DNA overlap between Neanderthals and modern humans is a remnant of a common ancestor

When scientists discovered a few years ago that modern humans shared swaths of DNA with long-extinct Neanderthals, their best explanation was that at some point the two species must have interbred.

Now a study by scientists at the University of Cambridge has questioned this conclusion, hypothesising instead that the DNA overlap is a remnant of a common ancestor of both Neanderthals and modern humans.

When the genetic sequence of Homo neanderthalensis was published in 2010, one of the headline findings was that most people outside Africa could trace up to 4% of their DNA to Neanderthals. This was widely interpreted as an indication of interbreeding between Neanderthals and early Homo sapiens just as the latter were leaving Africa. The two species would have lived in the same regions around modern-day Europe, until Neanderthals died out about 30,000 years ago.

But Andrea Manica said the analysis had over-estimated the amount of shared DNA between Neanderthals and humans that could be explained by interbreeding. The analysis had not taken into account the genetic variation already present between different populations of the ancestors of modern humans in Africa.

"The idea is that our African ancestors would not have been a homogeneous, well-mixed population but made of several populations in Africa with some level of differentiation, in the way right now you can tell a northern and southern European from their looks. The mixing is not complete within continents."

Taking these population differences, known as "substructuring", into account for early humans living in Africa, Manica and his colleague Anders Eriksson worked out that modern humans and Neanderthals must have shared a common ancestor some 500,000 years ago and that the subsequent evolution of this species was enough to account for the DNA crossover.

"There was an ancestor of both Neanderthal and modern humans – some archaeologists would call that Homo heidelbergensis – that would have covered Africa and Europe about half a million years ago," he said. "It wouldn't have been a single well-mixed population, it would have been like modern humans – populations that are closer to each other are more similar."

The results are published in the Proceedings of the National Academy of Sciences.

About 350,000 years ago, the European and African ranges of this last common ancestor became separate: the European range would later evolve into Neanderthals and the African range into anatomically modern humans, who left the continent 70,000 years ago to cover the world.

Prof Svante Pääbo, at the Max Planck Institute for Evolutionary Anthropology in Leipzig, who led the sequencing of the Neanderthal genome in 2010 and has championed the idea that modern humans interbred with Neanderthals, said he was surprised that Manica's work had been published, since his original paper had admitted a role for substructuring in Africa in the sharing of DNA between humans and Neanderthals. "But we regard this as a less parsimonious explanation," he said.

Pääbo has co-authored a paper, which is yet to undergo peer-review, to further support his thesis that humans and Neanderthals did in fact interbreed. "We find that the last gene flow from Neanderthals (or their relatives) into Europeans likely occurred 37,000-86,000 years before the present, and most likely 47,000-65,000 years ago," he writes. "This supports the recent interbreeding hypothesis, and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neanderthals as they expanded out of Africa."


Alok Jha, science correspondent

The GuardianTramp

Related Content

Article image
Study casts doubt on Neanderthal ‘flower burial’ theory
Exclusive: Bees may be source of pollen near remains but evidence still suggests bodies were buried with care

Linda Geddes Science correspondent

28, Aug, 2023 @6:00 AM

Article image
Leg bone yields DNA secrets of man's Neanderthal 'Eve'

Genetic material shows division of species between Neanderthal and humans occurred 660,000 years ago

Ian Sample, science correspondent

07, Aug, 2008 @11:01 PM

Article image
Scientists to grow 'mini-brains' using Neanderthal DNA
Geneticists hope comparing prehistoric and modern biology will help them understand what makes humans unique

Hannah Devlin in Leipzig

11, May, 2018 @1:42 PM

Article image
Human-Neanderthal relationships may be at root of modern allergies
Three genes inherited from our Neanderthal cousins may cause modern carriers to have an overly-sensitive immune system susceptible to allergies

Ian Sample Science editor

07, Jan, 2016 @5:00 PM

Article image
Did human women contribute to Neanderthal genomes over 200,000 years ago?
A recently published Neanderthal mitochondrial genome supports the hypothesis that there was an extremely early migration of a small group of African hominins, with whom they interbred.

Jennifer Raff

18, Jul, 2017 @2:34 PM

Article image
Lucy Mangan: wanted – mother for Neanderthal baby
'Don't you long, occasionally, for something really, really interesting, something different, something overwhelmingly "other" to happen?'

Lucy Mangan

26, Jan, 2013 @9:00 AM

Article image
Behind this Nobel prize is a very human story: there’s a bit of Neanderthal in all of us | Rebecca Wragg Sykes
Svante Pääbo deserves his accolade – palaeogenetics is an expanding field that tells us who we are, says archaeologist Rebecca Wragg Sykes

Rebecca Wragg Sykes

10, Oct, 2022 @5:00 AM

Article image
Neanderthal genes found for first time in African populations
Findings suggest human and Neanderthal lineages more closely intertwined that once thought

Hannah Devlin Science correspondent

30, Jan, 2020 @4:00 PM

Article image
My Neanderthal sex secret: modern European's great-great grandparent link
Genetic tests on one of earliest Europeans living 40,000 years ago finds unusually high DNA levels to reveal sex with Neanderthal only four to six generations earlier

Ian Sample

22, Jun, 2015 @3:00 PM

Article image
Neanderthals may have died of diseases carried by humans from Africa
New research challenges the idea that the spread of infectious diseases exploded as agriculture evolved 8,000 years ago

Maev Kennedy

10, Apr, 2016 @6:00 PM