And yet, the odds of a random adoptee growing up in the same city, choosing the same profession, favorite color, and rubber-band wearing habit are astronomically lower than those of an identical twin doing so.
Many twin studies, particularly those done in the past few decades have been rigorous. And the correlation in IQ, career and age of marriage between such twins, are far higher than those of siblings, or adopted siblings growing up in the same house.
There may be a political reason for rejecting the role of heredity or the large body of research supporting it, but there isn't a scientific one.
That's an anecdote, not a study. The criticism I leveled is at twin studies in general, not twin studies .
Heritability is very specific measure, and it does not mean "genetic". Zip codes are highly heritable; number of arms is not heritable at all. I refer you to a great article on the subject of what "heritable" really means in this context:
A single example of twins who are similar proves nothing. I've personally met identical twins who couldn't be more unlike each other - which is no more evidence than the single case (case study, anecdote, they mean the same thing) you cite.
The author works as a professor of statistics, and his work is specifically in the field of uncovering the latent variables which underly human achievement. His arguments seem cogent and clear to me. Just because he comes to different conclusions from you does not mean he "has an axe to grind", which is a purely ad hominem accusation. Where do you think he makes a mistake?
He has admitted that part of his skepticism is due to the fact that he doesn't like the concept of intelligence in a general sense. He is far more critical of claims of heredity than he is of environment. Even half the level of scrutiny he applies to twin studies would invalidate nearly the entirety of sociological research on account of "not controlling for genetics". That is why I say he has an axe to grind.
As for his credentials, he's an associate prof with little to no background in biology, psychology or the study of the brain.
Steven Pinker, on the other hand is a full professor at Harvard (formerly MIT), and is the world's premier on the subject he's writing on.
The only reason number of arms is not heritable is because the variance is close to zero.
Once you include a sample with non-trivial variance (a sample including humans, snakes and spiders), you discover that number of arms is almost 100% heritable.
You're missing the point. Saying something is "heritable" is essentially meaningless. It tells you how that trait would change in the group measured in response to evolutionary selective pressure, and that's it. It doesn't tell you whether the trait is genetic, it doesn't tell you whether the trait is important, and it doesn't tell you whether the trait even exists in a meaningful way.
You can measure quite decent heritability from entirely random traits:
Many twin studies, particularly those done in the past few decades have been rigorous. And the correlation in IQ, career and age of marriage between such twins, are far higher than those of siblings, or adopted siblings growing up in the same house.
There may be a political reason for rejecting the role of heredity or the large body of research supporting it, but there isn't a scientific one.