I know the standard argument for genetic influence on IQ relies heavily on twin studies showing high heritability. But identical twins raised apart are not perfectly correlated in IQ, which means something beyond genes is doing work. How much do separated identical twins actually differ in IQ and what does that tell us about the relative contributions of genes and environment to cognitive ability?
The separated twin data is actually one of the strongest arguments FOR genetic influence rather than against it, once you look at the actual numbers 
The Minnesota Study of Twins Reared Apart found IQ correlations of around 0.70 between identical twins raised in completely different families. That is remarkably high given that these individuals shared no common environment whatsoever after separation. The fact that they did not correlate perfectly at 1.0 is exactly what you would expect given measurement error alone, even before accounting for genuine environmental effects. The more striking finding is that separated identical twins correlate more strongly with each other than non-identical twins raised together in the same household. Sharing 100 percent of your genes with someone predicts more cognitive similarity than sharing a childhood with them 
The separated twin correlation of 0.70 is honestly kind of mind blowing when you sit with it 
These are people who grew up in completely different families, different schools, different cities, sometimes different countries, and their IQ scores still track each other at that level. Genes are clearly doing a lot of heavy lifting 