First, heritability estimates on which claims of natl inequality depend today only give a local analysis that depends ont enviromental conditions and the distribution of genotypes that happens to exist at a given time, as Lewontin underlined 25 yrs ago. Block then underlines that heritability tells us nothing about the effect of introduction environments that are either new or not now common. If we want to know the effects of a new or uncommon environment, we should ignore heritability and just try changing the environment. This is only one reason why the heritability estimate cannot be used to draw conservative policy implications, but even sociological critics Fischer, et al don't argue this. The word heritability doesn't even appear in the index of Inequality by Design, though that's the main statistic in Murray's book.
At the same, there is no denying that there are inequalities that will remain heritable or natural in some important sense in socialist or any conditions. Colletti argues: "Rousseau's argument is that society should take 'natural differences' into account, by recognzing and in some sense confirming them. Marx argues that society should do this not to confirm these differences but rather so as to be able to suppress dsiavantages by recognizing them, and therefore prevent 'unequal individual attributes and hence capacity to produce' operating--'tacitly'--as 'natural priviliges.'". Colletti then quotes from the German Ideology (it's p. 593 in the unabridged Moscow version):
"but one of the most vital principles of communism, a principle which distinguishes it from all reacitonary socialism, is its empiric view, based on a knowledge of man's nature, that differences of *brain* and of intellectual capacity do not imply any differences whatsover in the nature of the *stomach* and of physical *needs*; therefore the false tenet, based upon existing circumstances, "to each according to his abilities', must be changed, insofar as it relates to enjoyment in the narrower sense, into the tenet, "to each according to his need"; in other words, a *a different* form of activity, of labor, does not justify *inequality*, confers no "priviliges" in respect of possession and enjoyment."
yours, rakesh