A new study has just been released that is making a stunning claim that has huge implications about the history of mankind. The paper, published by Cell Press, states that although Neanderthals went extinct 30,000 years ago, they live today within us in our very DNA. In fact, Neanderthal DNA comprises about 2 percent of the genomes in modern day humans of European and Asian heritage.

Humans and Neanderthals split off from each other on the evolutionary tree about 700,000 years ago, but the two species continued to interbreed until about 50,000 years ago. While humans and Neanderthals had enough genetic differences that reproduction was difficult, it did happen, and as a result there is still some of the DNA in us today.

But the revelation also raises a lot of questions. We know the genes are there, for example, but scientists still have to figure out what these genes do and what traits they are responsible for. Some genes may have a big impact on us, while others may have very little. Still, this is a fascinating discovery that could lead to new revelations about our history down the road.

“Even 50,000 years after the last human-Neanderthal mating, we can still see measurable impacts on gene expression,” says geneticist and study co-author Joshua Akey of the University of Washington School of Medicine. “And those variations in gene expression contribute to human phenotypic variation and disease susceptibility.”

“We find that for about 25% of all those sites that we tested, we can detect a difference in expression between the Neanderthal allele and the modern human allele,” says the study’s first author, UW postdoctoral researcher Rajiv McCoy.