As i said, given an ideal environment, intelligence is purely genetic. This whole focus on environment is important, because we ought to have it right for our kids, but its like saying that a cars performance is about oil brands and road conditions. No, a better engine makes a better car and developing the engines is exciting and important because we know how to make good oil and roads and once the roads are paved and refineries operating, most of the progress will be understanding the engine. Yes you need roads but being able to understand and possibly select and manipulate genetics associated with intelligence will produce huge, groundbreaking changes that will make the world much, much better.
"Given an ideal environment" is a pretty big "given". You might as well say "given an ideal environment, X is purely genetic for any human characteristic X.
First, an anecdote about knowing someone smart related to a physicist means hardly anything. I happen to personally know two prestigious scientists (NAS, HHMI fellows) who both have children you'd consider very mediocre (one in his 4th year of community college).
I am not taking the position that genetics does not contribute to intelligence. Of course it does. Like you pointed out, humans are smarter than other species, like apes. What we are trying to determine here the degree to which systematic genetic variation within our own species contributes to intelligence. One thing we know for sure is that this claim...
> There is no doubt that intelligence is purely genetic.
I'm confused; what would it mean for that statement to be false? It sounds equivalent to "If everything non-genetic that can raise intelligence is present and everything non-genetic that can lower intelligence is absent, then the part that's left, the non-non-genetic component, is 100% genetic."
You're correct, but you're missing his point. The point is that genes do determine maximum intelligence---certain people simply cannot be as smart as certain other people, regardless of how good their environment is to them.
I think you're missing pjscott's point. Sure, a fixed set of genes determines the maximum intelligence across varying environments, but it's equally true that a fixed environment determines the maximum intelligence across varying genes. How is one or the other "the" maximum?
You can measure and modify the environment for a growing child/youth with relative ease; but you cannot modify genetic makeup at all (for now). This makes the distinction a valuable one.
Think of a car analogy: Genetics is the engine's size and type, environment is the fuel/tyres/lubricant that were added. Quite possible to get very bad performance out of a car with no engine oil or fuelled with diesel instead of petrol - but once these "hygiene factors" are addressed, the maximum performance is determined by innate factors.
People who shoot down science because it's racist/sexist/etc. are shooting down the truth. People who make overreaching claims are just as detrimental. I think intelligence is very largely genetic. Claiming its "purely genetic" only gives more fodder for the "that's racist"-types to shoot it down.