December 18, 2013
Evidence Shows Incest, Interbreeding Common Among Neanderthals
redOrbit Staff & Wire Reports - Your Universe Online
Genetic sequencing of DNA extracted from a Neanderthal woman’s toe bone reveals the species was not only incestuous, but also interbred with other types of human ancestors, according to research scheduled for publication in Thursday’s edition of the journal Nature.
An international team of scientists, including researchers from the University of California, Berkeley, completed what they are calling the most complete sequencing of the Neanderthal genome to date. Their analysis of the 50,000-year-old bone unearthed a long history of interbreeding amongst at least four different types of early humans.
According to Traci Watson of USA Today, the study authors found the Neanderthals, the Paleolithic-era Denisova hominins, and our own species had sexual relations with one another, “leading to children of highly mixed evolutionary heritage.” A fourth-type of human was likely involved as well, she added.
“We don't know if interbreeding took place once, where a group of Neanderthals got mixed in with modern humans and it didn't happen again, or whether groups lived side by side, and there was interbreeding over a prolonged period,” study co-author Montgomery Slatkin, a population geneticist at UC Berkeley, told AFP.
The study found between 1.5 percent and 2.1 percent of modern human genomes can be attributed to Neanderthals, with Africans (who have no genetic contribution from the Neanderthals) being the exception. The study also found the genomes of ethnic Han Chinese and other mainland Asian populations, as well as those of Native Americans, contain approximately 0.2 percent Denisovan genes, and that the Denisovans themselves received at least 0.5 percent of their DNA from Neanderthals, the French news agency added.
The more scandalous finding is the fact the sequencing revealed Neanderthals interbred with family members. In fact, as Ellie Zolfagharifard of the Daily Mail noted, the female whose toe bone was the source of the research found that her parents were either half-siblings that shared the same mother, or related in some other way (uncle/niece, aunt/nephew, grandparent/grandchild, etc.)
“We know these people were mixing with their close relatives. This seems to be something special about the Neanderthal population, it has this feature of inbreeding. We know this wasn’t a single event,” David Reich, a study author and professor of genetics at Harvard Medical School, told Bloomberg's Elizabeth Lapatto in a telephone interview.
He added there is speculation the lack of genetic diversity could have made these pre-humans less fit over the long term, possibly leading to their ultimate demise.
While it might be shocking to learn Neanderthals were incestuous, evolutionary biologist Mattias Jakobsson of Sweden's Uppsala University, who was not part of the study, told Dan Vergano at National Geographic that this discovery “is more of an anecdote… The more interesting observation would be if this mating behavior was common among Neandertals and/or Denisovans compared to [early modern humans] at that time.”
“The paper really shows that the history of humans and hominins during this period was very complicated. There was lot of interbreeding that we know about and probably other interbreeding we haven't yet discovered,” Slatkin added in a statement. “There is no gene we can point to and say, 'This accounts for language or some other unique feature of modern humans,’ but from this list of genes, we will learn something about the changes that occurred on the human lineage, though those changes will probably be very subtle.”