Okay, sapiens--time to meet the rest of the family

In my previous post on Solomon Island blonds, I brought up the unexpected relationship between New Guineans/Solomon Islanders and a fossil group of humans, the Denisovans. The evidence of Denisovans in the family tree of Oceania was the second such proof of modern human-fossil human mixing during prehistoric times, with the first study showing admixture between Neanderthals and pretty much everybody who isn't sub-Saharan African. Since Oceanians are definitely not sub-Saharan Africans, that means they've got both Denisovan AND Neanderthal ancestors, with the bulk of their genes being from a group that left Africa 50-60,000 years or so ago.

So, you might be asking, this is all well and good, but what the hell does it mean, exactly? First off...what's the difference between a fossil and a modern human?

Whew...ye gods, how do I brew this down into a few sentences? "Modern humans"--meaning people who look more or less like the sort of people you see wandering around now--originated in Eastern Africa 200,000 years or so ago. At the time of these earliest "modern humans" there were older populations of humans who'd left Africa a million or so years ago to inhabit Europe, the Middle East, and Asia. Since there was no little or no mixing between Africans and the people in Europe, Asia, etc. over the intervening 800,000+ years, the people on these continents had developed greater physical differences than Africans, Europeans, Asians, etc. possess now. These physical differences were sufficient enough that these regional human variations are usually considered to be not just different races, but different species altogether. Just as there are different species of parrots or dogs (domestic dogs, coyotes, wolves, etc.), two hundred thousand years ago there were several different species of humans.

Between the mid-1980s and last year, the majority of scientists considered these various human species unlikely to have successfully interbred. The modern humans who lived in East Africa finally decided to get off their caveman arses around 50-60,000 years ago and go check out the rest of the planet, and when they did they were so superior to the older human forms that they simply wiped them completely out.

This hypothesis, called "Out of Africa" received a bit of a serious blow in early 2010, however, when it was shown by scientists at the Max Planck Institute in Leipzig, Germany and UC Santa Cruz that modern human DNA could be shown to have Neanderthal ancestry. The older idea of us moderns tromping out of Africa and hunting down the hapless, stupid, and hairy Neanderthals was out. Our ancestors had made love, not war, and the evidence could still be shown in Europeans, Chinese, and Papuans.

The picture of human prehistory got even messier in December 2010, when researchers sequenced the DNA from a fossil finger bone and a tooth. They were able to show that the owners of the finger and tooth were not Neanderthals, as they expected, but a second group of humans that had been isolated from the Neanderthals for 500,000 years or more. Since the relics came from a came in southern Siberia known as Denisova Cave, these people have come to be known as the Denisova Hominids--and their DNA was still apparent among the living people of Oceania.

So, got all that?

Next up, we'll get to actually meet the fossil humans whose neighbourhoods our thoughtless, boorish ancestors blundered into all those years ago.