Thanks for the link.
If I understand correctly, the inheritability of a trait often increases with a decrease of environmental variability.
In this study they are comparing cattle raised in modern times in a developed country (the Netherlands, I think), hence the environment was likely about optimal, and unsurprising most of the observed phenotypic variation had a genetic origin.
Ethiopian subsistence farmers probably don't have access to cheap soy and corn and have their cows graze on marginal lands, therefore nutrient availability is likely the limiting factor in their milk production.
Similar patterns can be found in traits like human stature and IQ, which are more inheritable in developed countries rather than in third-world countries, and are subject to quick bursts when a country becomes more developed.
Also, in the modern dairy industry, cows are slaughtered around the age four and sold for beef, while in subsistence farming they are likely to be kept for many years past peak milk production, resulting in lower lifetime averages.
As for the specific of the inheritability of a continuous trait, I'm not an expert of genetics, but it seems to me that a polygenic model makes intuitive sense, as was quantitatively confirmed by this study.
They found that a non-linear model predicts the data better than a linear model, which is however quite good, and again I don't find this particularly surprising since linear approximations often perform well on sufficiently smooth functions, especially in the neighbourhood of a stationary point (where you can expect the genotypes of a relatively stable population to be, approximately).
My problem with Hsu line of argument is that he extrapolates predictions of these kinds of linear models way past observed phenotypes, which is something that has no theoretical basis, especially given that non-linear effects (logarithmic and logistic responses, square-cube effects, etc.) are ubiquitous in biology.
If I understand correctly, the inheritability of a trait often increases with a decrease of environmental variability.
Yes. (More relevantly, I'd say that as the environment gets better, the heritability will increase.)
Overall, your points about the Ethiopian cows are correct but I don't think they would account for more than a relatively small chunk of the difference between the best American milk cows and regular Ethiopian milk cows. It really does look to me like humanity has pushed milk capacity dozens of standard deviations past where it would have ...
Vincent Müller and Nick Bostrom have just released a paper surveying the results of a poll of experts about future progress in artificial intelligence. The authors have also put up a companion site where visitors can take the poll and see the raw data. I just checked the site and so far only one individual has submitted a response. This provides an opportunity for testing the views of LW members against those of experts. So if you are willing to complete the questionnaire, please do so before reading the paper. (I have abstained from providing a link to the pdf to create a trivial inconvenience for those who cannot resist temptaion. Once you take the poll, you can easily find the paper by conducting a Google search with the keywords: bostrom muller future progress artificial intelligence.)