For more, see the OpenCourseWare 7.012 page. Transcript for this lecture is here.
Weinberg (@ 32:40): ... And what happens if one of these days people discover alleles for certain aspects of cognitive function? Chess playing ability. The ability to learn five different languages. The ability to remember strings of numbers. The ability to speak extemporaneously in front of a class, for what it's worth, for 50 minutes several times a week.
[It seems improbable to me that such abilities will be controlled or strongly impacted by specific alleles. Rather, they are likely to be subtly influenced by large numbers of different genetic loci. But this doesn't necessarily affect the following discussion. Note also that Weinberg neglects the possibility of variation in direction of selection pressure experienced by different isolated groups.]
Whatever ability you want, valued or not so valued, what if those alleles begin to come out? And here's the worse part. What if somebody begins to look for the frequency of those alleles in different ethnic groups scattered across this planet? Now, you will say to me, well, God has made all his children equal. But the fact is if you look at the details of human evolution, some of which I discussed with you a week ago, last week, you'll come to realize that most populations in humanity are the modern descendents of very small founder groups.
... So the fact is it's inescapable that different alleles are going to be present with different frequencies in different inbreeding populations of humanity or populations of humanity that traditionally have been genetically isolated from one another.
It's not as if all the genes that we carry have been mixed with everybody else's genes freely over the last 100,000 years. Different groups have bred separately and have, for reasons that I've told you, founder affects and genetic drift, acquired different sets and different constellations of alleles. So what's going to happen then, I ask you without wishing to hear an answer because nobody really knows?
Then for the first time there could be a racism which is based not on some kind of virulent ideology, not based on some kind of kooky versions of genetics, because the eugenicists in the beginning of the 20th century, as well as the Nazis hadn't had any idea about genetics, they were just using the word, even though they knew nothing about the science of genetics as we understand it today. But what happens if now for the first time we, i.e., you who begin to understand genetics, begin to perceive that there are, in fact, different populations of humanity that are endowed with different constellation of alleles that we imagine are more or less desirable?
What's going to happen then? I don't know. But some scientists say, well, the truth must come out and that everything that can be learned should be learned, and we will learn how to digest it and we will learn how to live with that. But I'm not so sure that's the right thing. And you all have to wrestle with that as well. ...