People today are mosaics, our genomes are rich tapestries of intertwined ancestors. With each fossil discovered, with every DNA analysis performed, history becomes more complicated: We, the only survivors of the genus Homo collect genetic fragments from other closely related but long extinct genera. Modern humans are the product of a spreading history of change and dispersion, division and union – a story characterized by far more diversity, movement and blend than it seemed possible a decade ago.
Original story, reprinted with permission from Quanta Magazine an editorial-independent edition of the Simons Foundation whose mission is to improve public understanding of science by embracing research and trends in mathematics and the physical sciences and sciences .
But one thing is to say that the Neanderthals interfered with the ancestors of modern Europeans, or that the recently discovered Denizans interfered with some older mysterious group, or that they all interfered with one another. Another is to provide specific details about when and where these compounds originated. "We have this picture where these events happen everywhere," said Eileen Scully, an evolutionary geneticist at Cambridge University. "But it is very difficult for us to attach some specific separate event and say, yes, we are really sure it happened ̵
You think you're just looking at the Neanderthal, but you're actually looking at a mix of Neanderthal and modern man.
Adam Sipel, Cold Spring Harbor Laboratory
Therefore, limited events tend to be relatively recent, beginning with the migration of modern humans out to Africa 60,000 years ago, during which they communicated with hominin relatives (such as Neanderthals and Denisans), they met along the way. Evidence of crossbreeding during any migration before or during events that occurred earlier in Africa is elusive.
Now that is starting to change. In part because of the higher computing power, "we're beginning to see the next wave of method development," says Joshua Ackay, a professor of genomics at the Princeton University Institute for Integrative Genomics. "And that allows us to start making new findings from the data … that the previous generation of methods couldn't do."
As scientists look back in time and reveal evolutionary connections in unprecedented detail, their discoveries complicate the narrative of human history and the salvation of some previously extinct chapters of suspense. There are indications of the unexpected influence of the gene flow of ancient hominas on modern human populations before the latter left Africa. Some researchers even identify the genetic contributions that modern humans could make to these other genera, in a complete reversal of the usual scientific focus. As confusing and intertwined as these many effects can be, they all shape humanity as we now know it.
Old people, new tricks
When researchers first extracted DNA from Neanderthal bones, the available techniques for making sense of it were powerful but relatively simple. The researchers compared ancient and modern sequences, combined shared sites and mutations, and performed group statistical analyzes. Thus, they discovered in 2010 that Neanderthal DNA accounts for approximately 2 percent of the genome of humans of non-African descent today, the result of cross-breeding that occurred across Eurasia, dating back 50,000-60,000 years ago. That's why they found that Denizovan's DNA made up about 3 percent of the genome of humans in Papua New Guinea and Australia.
"But this kind of very simple approach is not very good at sorting out the complexity" of how lost populations interact, said John Hawks, a paleoanthropologist at the University of Wisconsin, Madison. In addition, it does not allow researchers to test specific hypotheses about how this crossing occurred.