People find that trivial and besides the point because they want control over it, especially if it’s disease-related and to get that you need the tyranny of behavioral genetics.

And a somewhat hastily written thought:
It seems recently that there have been astounding technological advances in science, particularly genetics, as well as a better scientific awareness in lay people. These two things seem to have combined into a sociological demand for empirical proof–that we measure and provide evidence for the latent variables we’ve long assumed to exist; such variables include “additive genetic variance” in genetics, “general factor (g) of intelligence” in psychology, “quality of life” in economics ” and “frailty” in demography. In some cases there is actually a technological way to measure and get at the latent variable we’ve assumed to exist, for example when we find a particular genetic marker of additive effect causally associating with a phenotype, but in other cases there is not a straight forward mechanistic relationship between the latent variable and its presumed causal influence on the things we can actually measure. For example, while we assume that “g” controls aspects of intelligence, describing how g does this is not something that we can empirically point to in the brain.

Some well-intentioned – but lacking good scientific data and/or extremely willing to substitute superstitions of class and race for proof – souls practiced eugenics, and tainted the idea (probably) forever.

Others promised a rapid agrigenetic revolution in the former Soviet Union, delivered next to nothing, and ended up in jails, with the whole enterprise of genetics condemned and substituted by neo-Lamarckism for over 20 years.

And more recently, underpowered candidate gene studies, shooting for SNPs associated with multiple IQ poin effects, yielded “statistically signifcant” flukes thanks to liberally applied multitesting, and now Chabris tries to salvage the tainted reputation of IQ genetics, but my guess is that the field will remain tainted for some time to come.

What happens afterwards (after your corresponded has already mentally equated a heritability study with the old wives tales) sort of depends on what one thinks about this specific “old wives’ tale”. If the old belief contradicts with this person’s body of beliefs, then woe to genetics, it must be as stupid and as wrong as the “old wives”. I venture to guess that your software engineer corresponded was concerned about some mental ability or societal success trait … areas where we’ve been acculturated to believe in equal abilities / 100% power of nurture, and to reject the traditional, discriminatory crackpot lore.

And, yet, when scientists do discover an allele of profound impact on an important behavior, though it be rare in all but black people, four years can go by before it receives meaningful attention again (after some direct persuasion from yours truly). Therefore, I would say that the GWAS jihadists have had a rather successful campaign to silence candidate gene research. What little research this allele has received was through low-cost data mining of an existing database, but I would expect that to change now that MAOA is also a cancer gene.

I think they actually want a specific gene before they accept that the geneticists have anything non-trivial to say about a trait. They actually knew all along that like anestors, like progeny; and a nearly-continuous, sort of low-penetrance polygenic model of inheritance is very intuitive. People are very much at ease with terms such as “1/8th of one’s great grandfather’s blood” etc.

One of the biggest surprises of genetics comes when it turns out the inheritance is actually highly discrete, all or none; or when it follows along intuitively unexpected lines, like X-linkage or even something as simple as heritability of male traits through mothers or female traits through fathers. Now that doesn’t resemble simple “serial dilution of blood”, and the listeners are like, aha, now the geneticists have something to tell us what we didn’t already know!