Arev Sümer, a paleogenetics PhD student at the Max Planck Institute for Evolutionary Anthropology in Leipzig, and Benjamin Peter, a population geneticist at the University of Rochester, have published two papers in Nature and Science that clarify the ancestral timeline of human evolution. They found that humans once had a smaller footprint, with early modern humans and Neanderthals having babies. The timing of this ancient interbreeding has been somewhat fuzzy, but the researchers have now pinned the period of interbreeding to sometime between 43,500 and 50,500 years ago.
The challenge of studying early hominids is that specimens from that period are scarce and in rough shape. Researchers used a new computational approach, comparing beat-up DNA sequences from 59 ancient humans living thousands of years ago, primarily in Eurasia, to good quality DNA sequences from a few Neanderthals and 275 people today with very little Neanderthal ancestry. They also worked with rare well-preserved early human remains from Germany and the Czech Republic, including the best preserved paleolithic bone from an early modern human ever found.
Sümer found that 3% of the DNA of these early humans came from Neanderthals, pointing to more recent Neanderthal ancestry. This constrains quite a few other things about human migration patterns, including when early humans migrated and who these communities were and how they diversified.