When history gets complicated

Razib posts some thoughts on how the study of human migration history has gotten more and more complex during the last fifteen years.

Sometimes I wonder if the period between the publication of The History and Geography of Human Genes and The Journey of Man, roughly from the mid-90s to the early 2000s, will be seen as a golden age for historical population genetics in hindsight. A few weeks ago I pointed to new data based on DNA extraction which really confuses the picture of how Europe was populated over the past 25,000 years. It seems the more data we get, the more interesting things get. In the late 1990s the emergence of powerful technologies to extract and amplify genetic material and sequence it shed light on several questions which had long tantalized researchers ever since Alan Wilson's group began to push the frontiers of molecular evolution in the 1970s. Where in the 1980s there was only the mitchondrial Eve story, by the year 2000 there was enough to go around for several books. The Journey of Man, Mapping Human History and The Seven Daughters of Eve all came out very close together chronologically. These scientists and writers knew that striking fast was imperative.

That’s also when Colin Renfrew’s “archaeogenetics” really got going, with a number of symposia and a couple of books. So what happened? As Razib points out, things got complicated – we started adding more autosomal markers, and larger samples of mtDNA and Y chromosomes, and the trees didn’t line up so cleanly. In retrospect this was predictable, as one-locus genealogies have so much variance that it’s easy to confuse noise for signal.

Heck, it’s not just hindsight, the problem was predicted at the time, by me and others!

Still, I’ve learned to appreciate science’s self-correcting nature. Phylogeography grew into a serious science, not flawless, but driven increasingly by testing hypotheses instead of promoting “consistency” with them. This happened partly by extending the same genetic techniques to other species, where the basic modeling questions didn’t have the same headline-grabbing emotional appeal as in humans.

Many shark-jumping moments of human genetics are still out there, waiting to be re-evaluated with new evidence.