Wired for Culture: Origins of the Human Social Mind by Mark Pagel Read Free Book Online Page B

certainly some of each. But startling recent evidence reveals that not all of our contacts with these people would have been warlike; some might even have been amorous. A few of the Neanderthal skeletons and the sole Denisovan fragments come from individuals who died recently enough in our past to fall within the range of time that it is possible to extract ancient DNA from their bones. A careful comparison of the complete genomes of these Neanderthals with those of modern humans, and a similar comparison between modern humans and the new Denisovan species, suggests that we might have interbred with both of them. If we did, some might find it reassuring to note that the evidence indicates the contact was limited: modern humans share around 4 percent of their genome with Neanderthals and Denisovans. This is to say that against the background of our genomes being approximately 99 percent or more similar to these species anyway—reflecting our recent divergence from a common ancestor—there are regions whose precise genetic signature gives them away as being even more recently shared.
    But there is a further twist. Current evidence indicates that interbreeding with these archaic Homo species occurred in two brief episodes. One episode happened possibly in the Near or Middle East shortly after a subset of modern humans left Africa. The second occurred further to the east, probably near to where the Denisovan fossils were found, and only in ancestors of modern-day Melanesian and Australian Aboriginal people. Spectacularly, neither signature of interbreeding is observed in people of African descent. So, we learn that the descendants of modern human populations that migrated out of Africa are mongrels owing to dalliances that occurred while their ancestors were trekking their way around the world. Intriguingly, when the genetic analyses revealed that Neanderthals had red hair, speculation arose as to the origin of red hair in some modern-day Scottish people—it is, after all, an unusual human trait. But the Scots can rest easy knowing that at least this part of their heritage did not come from Neanderthals—the gene causing red hair in modern humans differs from that in Neanderthals.
    The era of our occupation of the world might have been a time when sightings of yeti, abominable snowmen, bigfoots, and possibly even hobbits were common, because there would have been at least three and perhaps as many as six distinct human species simultaneously walking the Earth. In addition to ourselves, the Neanderthals, the remnants of Homo erectus and Denisovan populations in Asia, and an unnamed archaic Homo species in India, there was possibly one other. Homo floresiensis , discovered in 2004 and nicknamed “Hobbits” by newspaper editors straining for a headline, stood around three feet tall. These tiny upright apes lived in caves in an isolated pocket deep in the jungles of the Indonesian island of Flores, possibly until 17,000 years ago. Nobody can be sure but they appear to be a dwarfed and small-brained descendant species of the H. erectus populations that had left Africa. Features of their anatomy, at least, indicate they are a separate branch of Homo evolution to our own. They almost certainly survived longer than the other competitors to modern humans by staying out of sight—there is no evidence that modern human populations ever made contact with them.
    After around 28,000 years ago the only places left on Earth for modern humans to occupy had never before seen human species of any kind. By around 18,000 years ago, groups of what we would now think of as Siberian people moved north and east into a large landmass known as Beringia that had been exposed when sea levels dropped during the last Ice Age. Beringia connected what is now present-day Russia and Alaska, allowing these Siberian people to walk into the Americas. They quickly colonized the northern and southern landmasses of this large continent that spanned nearly the