Is intelligence hereditary?

There is a tremendous amount of empirical research clearly showing that intelligence is hereditary. The estimates range somewhere between .50 to .80 (and are likely closer towards the latter). Obviously, each line of research on this topic (e.g., twin studies, adoption studies, GWAS) has its own specific limitations. Yet, despite such limitations, the different lines of research converge on the conclusion that intelligence is heritable.

The type of evidence comes from many directions. Just to name a few prominent ones:

1) Twin studies that distinguish between genetic and environmental aspects show a substantial heritable component.

2) Adoption studies show that the intelligence of the adopted child more strongly resembles the intelligence of the biological parents than the adoption parents.

3) The heriability coefficient of intelligence actually increases with increasing age. Which would not be expected if it is mainly the environment that would have the strongest influence.

There still may be some debate about the exact estimate of the heritability coefficient (for example, whether it is more closely to 60 or to 80%). But, based on the available evidence that has been collected during the last hundred fifty year or so, I don't think that there can be much doubt that intelligence is quite strongly heritable.