The topic this year was the return of scientific racism — basically, the way science is being increasingly misused to support racist idealogies. The lecturer was Adam Rutherford, a geneticist who presents Inside Science on Radio 4.
Geneticists don't have much time for the concept of race, because it makes no sense scientifically. If you do cluster analysis on gene markers, there are as many races as you ask for clusters (and some of them are pretty small: the new "race" that appears when you increase clusters from 5 to 6 consists entirely of a tribe of 4,000 or so people living in the Himalayas). Explanations regarding how people of some ethnic backgrounds do better at some sports than others are almost always flawed: the reason there are so few African-American Olympic swimmers is nothing to do with bone density and everything to do with the fact that only 30% of them are taught to swim.
I was left wondering whether even what I thought were relatively uncontroversial statements about what people associate with "race" are true or not. For example, I wouldn't have thought it too provocative to suggest that levels of vitamin D production and protection against ultraviolet light are both informed by how light or dark your skin is, but I'm now thinking that even this really needs a citation or two to back it up.
One really interesting concept I did pick up on that I'd not come across before was the isopoint, also known as the identical ancestors point. So, if you look back at how many ancestors you have, it's 2 for one generation, 4 for two, 8 for three and so on. It's 2n, where n is the number of generations you look back. Unfortunately, when you look back, say, 40 generations, 240 is more than the number of humans who have ever lived. What happens is that you start to get cross-overs in family trees. The further back you go, the more of these there are. If you go back far enough, you reach a point where everyone who was alive and who has living descendants today is an ancestor of all individuals who are alive today. This is the isopoint.
It turns out that for people of European heritage, that isopoint is surprisingly recent: the tenth century. Every European alive in the tenth century who has a living descendant is an ancestor of all living Europeans. Worldwide, the average isopoint is about 5,000 years ago. Everyone alive today is descended from everyone alive 5,000 years ago who has any living descendents at all.
Those are the figures Dr Rutherford gave, anyway. Wikipedia puts the isopoints later, but Wikipedia isn't a geneticist.
It's nice to know that I'm a direct descendant of every tenth-century European monarch who has direct descendants.
Oh, it turns out that Voltaire himself was rather more racist than his contemporaries, making this a somewhat ironic entry in the Voltaire Lecture series.