Jonah Goldberg asks:
Why does the Left get to pick which issues are the benchmarks for “science”? Why can’t the measure of being pro-science be the question of heritability of intelligence?
I don't know much force this question has: maybe some lefties do reject the heritability of IQ on ideological grounds. I want to make another point - that there's no need for them to do so. You can accept that IQ (or ability generally) is heritable and still be a strong egalitarian.
I say this because of a simple principle: luck egalitarianism. This says that inequalities are unjust if they are due to circumstances beyond one's control. If we grant that ability is inherited, then differences in ability are obviously a matter of luck. Insofar as these give rise to inequalities of income, a luck egalitarian can thus claim they are unjust.
In this context, Tim's claim that the high intergenerational elasticity of wealth (pdf) uncovered by Greg Clark might be due to inherited ability rather than inherited wealth is irrelevant. The luck egalitarian can reply: it doesn't matter whether what is inherited is wealth, ability, cultural capital or whatever. Whichever it is, it's a matter of sheer luck and thus unjust. There is therefore a moral case for equalizing such inequalities - though whether there's an economic case is another matter.
And sure enough, there is some evidence that our economic fate is heritable. Not only do we have Clark's findings, but there's also evidence of high heritability of long-term incomes, and evidence that savings rates and hence late-life wealth inequalities are partly genetic.
That said, there is a sort of leftie who would be discombobulated by the heritability of ability. I'm thinking of that sort, like Tessa Jowell, who - in their optimism about the malleability of humankind - think that education can significantly reduce inequality.
Of course, some of you might want to reject luck egalitarianism; feel free to argue against Richard Arneson's defence (pdf) of it: surprisingly, laboratory experiments show that few people actually are luck egalitarians.
My point, though, is merely that there's no conflict between leftism and a belief in the heritability of ability. In this respect at least, the left has nothing to fear from science.