Analysis of two Neanderthal genomes, one Denisovan genome, and four modern human genomes revealed new evidence of gene flow between these species, further confirming previous work that suggests that they mated with one another.
The team found that three percent of the Neanderthal genome came from interbreeding with ancient humans. They estimate this intermixing happened between 200,000 and 300,000 years ago — far earlier than previous estimates indicated.
They also found that one percent of the Denisovan genome contained genetic material that came from an unexpected source – an “archaic human ancestor” that was neither human, nor Neanderthal, nor Denisovan.
The authors suggest that 15 percent of genetic regions that came from that archaic ancestor have been passed on to humans today, and there are a few theories as to who it came from and how it got baked into our genetic code.
The team proposes that this archaic human ancestor could be Homo Erectus.
At this point the authors know one thing for sure: “it may be reasonable to assume that genetic exchange was likely whenever two groups overlapped in time and space,” they write.
That is, if any two species found themselves in the same place at the same time, they were probably getting it on.