Interbreeding with Homo sapiens may have played a key role in the extinction of Neanderthals, a new study suggests.
This could have reduced the number of Neanderthals who reproduced among themselves, eventually leading to their extinction, according to a new study published in the journal “Paleoanthropology.”
“For a long time, the main theory was that intense competition between Homo sapiens and Neanderthals for resources led to their demise,” said Dr. Lucy Crit in an interview with the BBC.
However, the new study conducted by Dr. Crit alongside Professor Chris Stringer, lead researcher at the Natural History Museum in London, suggests that it wasn’t violence that weakened the Neanderthal gene pool, but rather the mixing of populations.
“We hypothesize that this behavior could have led to the extinction of Neanderthals if they regularly interbred with Homo sapiens, eroding their population until they eventually disappeared,” Professor Stringer explained following the study’s publication.
Neanderthal DNA can be found in everyone alive today, including people of African descent, whose ancestors were thought not to have come into direct contact with this group.
Neanderthals and Homo sapiens evolved in different parts of the world after diverging about 600,000 years ago.
While Homo sapiens evolved in Africa, Neanderthals lived in Europe and Asia.
“Recent findings show that Homo sapiens were present in Europe around 50,000 to 60,000 years ago, meaning they coexisted with Neanderthals much longer than we previously thought,” Dr. Crit explained.
Neanderthal genomes have been found in the genome of Homo sapiens, but not vice versa, the study reveals.
“It seems there was gene exchange, but only in one direction,” Dr. Crit explained.
We already know that these two species interbred—if you were born outside of Africa, approximately two percent of your genome comes from Neanderthals.
However, Dr. Crit and Professor Stringer delved deeper into the subject by analyzing what is known about the 32 Neanderthal genomes that have been found and sequenced so far.
The two scientists suggest that the success of interbreeding depended on the specific pair involved.
“But we don’t know how to fully explain this. It may be due to the available data or the way hybridization (the process of mixing two species) works,” Dr. Crit said.
“In some species of birds and mammals, hybridization doesn’t always work both ways: it can be difficult for one species to produce fertile offspring,” she added.
She hopes that more Neanderthal fossils will be discovered and analyzed in the future.
“The more we can sequence and analyze, the more we can test these theories,” she said.
Another theory presented by Dr. Crit and Professor Stringer in the study is that not all sexual encounters may have been consensual.
“Homo sapiens may have sought out females from the other group or vice versa, using force to find fertile representatives,” Dr. Crit stated.
She explained that this type of behavior can also be observed in some chimpanzees.
“If males do not have enough reproductive females in their own group, they may go to another group and abduct them for breeding,” she said.
However, very little is actually known about such encounters.
Scientists believe that it wasn’t easy for Neanderthals and Homo sapiens to communicate, as they were quite different from one another.
“They probably couldn’t produce the same types of sounds, they didn’t have the same kind of articulated speech, and their brains were structured differently,” Dr. Crit explained.
Their physical appearance was also different.
“Neanderthals were quite stocky, heavily built, with shorter arms and legs, and they had a characteristic protruding brow ridge above their eyes,” Dr. Crit added.
However, it still isn’t clear how different male and female Neanderthals were.
“The skeletal remains are usually fragmented and broken, and we don’t have enough pelvises to compare and see differences between them,” Dr. Crit said.
Despite many unknowns, Dr. Crit is excited about the potential for future discoveries, as reported by the BBC.
“New methods have allowed us to do things we couldn’t have imagined before,” Crit said.
“It’s like a giant puzzle. Sometimes it just keeps getting bigger and bigger with new discoveries that change the way we think.”