Our Denisovan Cousins

The July issue of National Geographic Magazine describes an amazing story of the recent discovery of yet another species of our human family that went extinct tens of thousands of years ago: the Denisovans. Remarkably similar to the Neanderthals, the Denisovans were a human subspecies that left Africa long before our species Homo sapiens did. They spread fairly widely throughout Eurasia and then died out. And, like the Neanderthals, they left traces of their DNA in us modern humans. In other words, our human ancestors seemed to be attracted enough by these extinct cousins of ours to have interbred with them, which finds us continuing to carry around a little of their DNA.

I find the story of human evolution fascinating. The narrative has been spectacularly amplified in recent years through evermore precise genetic measurement tools. Where anthropologists were once confined to detailed examination of the shape and appearance of fossil skeletal remains, they now can perform exacting genetic analyses of the tiniest of bone fragments.

Before 2008 we were completely unaware that a subspecies like the Denisovans even existed. Their population appears to have been rather small and no identifiable bone fragments had ever been found. Then, five years ago, digging in a cave that had repeatedly been used by people over the eons, a Russian archeologist discovered a miniscule bone fragment in a Siberian cave called Denisova. Had the discovery been made just a few years earlier, it is unlikely that this wee fragment would ever had led to the realization that it was from a previously unknown prehistoric species of human. 

Cutting-edge DNA analytical methods that have recently been developed in Germany (Max Planck Institute) were able to construct the complete genome of the person from whom the bone fragment came: the left pinky finger of an eight-year-old girl. (They even got a pretty good idea of the color of her hair!) In fact, these techniques have become so precise that the girl's genome could be probed to the extent that researchers could even describe the different genetic contributions she received from her father and mother. From a bone piece the size of a dried bean!

The speed with which our evolutionary history is being filled out is astounding. Scientists are discovering that our origin is far more complex and rich than we'd ever have guessed. Anthropology is as exciting a field as cosmology these days, as the rate of new discoveries is so great that specialists in these fields have a hard time keeping up—let alone us average beings.

It makes me wonder about the even better research tools that will very soon become available, and the wonderful stories that they will reveal about the nature and origins of our universe and all its marvels. I am getting perilously close to my 73^rd birthday, which causes me to increasingly reflect upon my mortality and how little time I have left to learn about all these neat things. At my age I take great comfort in knowing that the pace of discovery has picked up as much as it has. Hasten on, science!