When I was growing up, it was understood that humans and Neanderthals were alive at the same time, but it was assumed the humans had “triumphed” somehow, by staying alive, while Neanderthals went extinct.
As humans have gotten better at understanding DNA, though, we’ve discovered there are some Neanderthal traits that are still with us, probably because our early ancestors got busy with the other humanlike species. Neanderthal lifespan was similar to that of early modern humans, and their childcare habits mimic what we ask modern mothers to do today. So yes, some 20 percent of their DNA has survived with us, though only 2-4 percent occurs in each person of non-African extraction.
While we’re celebrating Neanderthals, though, we shouldn’t forget our lesser-known relatives, the Denisovans, the third major hominid group to migrate out of Africa. We were probably doing some fooling around with the Denisovans, too. They’re more recently-discovered than the Neanderthals, and were made a separate species in 2010 when their DNA was shown to be different from the other, better-known hominid cousin.
In fact, our family tree has been reshaping quickly due to advances in sequencing DNA. Another, more-ancient ancestor was discovered in 2011. Called Australopithecus sediba, the hominid may represent an intermediate step between the more ape-like Australopithecus family and modern Homo. The origins of Homo (we’re Homo sapiens) are still mysterious, and further work on Au. sediba may help us understand our origins. While they walked upright, like modern humans, they also liked bark so much they ate it.
The Neanderthal discoveries were made by comparing the Neanderthal reference genome to the genomes of hundreds of modern humans. Given that we also have a model Denisovan genome sequence, it seems likely that applying the same methods from the Neanderthal study could tell us how indebted to Denisovans we really are. And who knows, perhaps there’s another Au. sediba lurking out there to throw a wrench into things when we get too comfortable.