A genetic analysis algorithm developed by scientists has revealed that today's humans carry the genes of an unknown ancestor due to hominin species intermingling hundreds of thousands of years ago.
The scientists also found more evidence that ancient humans and related species crossbred various times, thanks to the remnants inside our DNA.
We know that some humans migrated out of Africa and crossbred with Neanderthals in Eurasia approximately 50,000 years ago. However, this new study shows that that was not the only instance where our human ancestors and their relatives interbred with each other, exchanging DNA.
The research, conducted by Melissa Hubisz and Amy Williams of Cornell University and Adam Siepel of Cold Spring Harbor Laboratory, was done to analyze genomes from two Neanderthals, a Denisovan, and two African humans to identify segments of DNA that came from other species. This was done with the use of an algorithm, developed by them.
The results were surprising, to say the least. First of all, it was seen that 3% of the Neanderthal genome could be traced back to ancient humans and that the interbreeding had happened between 200,000 and 300,000 years ago.
Another finding was that 1% of the Denisovan genome was determined to have come from an unexpected source – an "archaic human ancestor" that was neither human, nor Neanderthal, nor Denisovan.
According to the team's estimates, about 15% of these "super-archaic" regions might have been passed down to modern humans, continuing to exist in the genomes of people today.
This archaic human ancestor could be Homo Erectus, the team proposes and writes, "It may be reasonable to assume that genetic exchange was likely whenever two groups overlapped in time and space."
The findings are published in the journal PLOS Genetics.