See: http://www.nyu.edu/econ/user/bisina/Chapter5_Sacerdote.pdf Excerpt: "Surely it would be difficult to deny that genetic effects matter. Just look at how much more biological siblings resemble each other on education and income than do adoptive siblings."

So maybe genetics is not the most important ingredient, but saying genetics is not relevant to this discussion is astounding. Smarter parents beget smarter kids -- that's not a controversial statement. IQ is heritable to a large extend. Smarter parents tend to be wealthier. (This is not true everywhere, but it is mostly true in the USA, the land of opportunity.) Smarter kids do better in college. That's not a controversial statement either.

I don't know about _most_ important, but genetics is definitely a large factor. Quoting from Heritability of Lifetime Income[1]

> we find that 24% (54%) of the variance of women’s (men’s) lifetime income is due to genetic factors and that the contribution of the shared environment is negligible

The Promises and Pitfalls of Genoeconomics[2] sees similar results, coming up with 46% and 58% heritability in women and men, respectively.

There's plenty of research here. "Heritability of income" is a good search term.

[1] https://helda.helsinki.fi/bitstream/handle/10138/38881/HECER... [2] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3592970/

""Humans are descended from monkeys" / "The Earth goes round the Sun" / … is a pretty extraordinary claim, and extraordinary claims require extraordinary evidence."

Dismissing as "extraordinary" any claim to which you are politically opposed is not good science. (Frankly, the Sagan quote is in itself not good science until you can get everyone to agree on what is "extraordinary".)

Meanwhile, an entirely appropriate riposte to GP would have been: ""Genetics is the most important ingredient here." is a claim, and claims require evidence."

Look at Plomins studies. Home environment has almost zero correlation.