"'Studies have shown that identical twins who grow up in separate families have an IQ correlation of 0.74, while adoptive siblings have no more similar IQ than strangers.' ... First off the bat, such studies are obviously social science, not science."

This is an important and legitimate way to estimate broad-sense heritability. It won't control for environmental effects within the womb, or cultural effects, but it's pretty strong science absent those criticisms.