A study published Friday in the journal Science Advances shows that just a sliver of our genome is uniquely shared with other humans, and not shared by other extinct groups like Neanderthals and Denisovans.

The rounded back is just like a modern human's; Neanderthals have a bulge at the back of the skull that almost resembles a hair bun. The oldest known fossils of early humans were found at Jebel Irhoud in Morocco, dating to 315,000 years ago. At the time when modern humans and Neanderthals lived there separately, sea levels were lower. Given the fact that the modern human skull is older than the Neanderthal skull, which was unexpected, researchers believe that a group of modern humans lived in the area but didn't thrive. Previous discoveries of early modern human fossils in Israel, dated between 90,000 and 194,000 years ago, could also represent populations that failed to thrive after leaving Africa.