The intelligence, innate or acquired?

The intellectual capacity does not depend on a pair of genes, but several. Is it innate or acquired? If we look at the genealogy of some families, could be tempted to believe in the legacy of talent.

Some scientists point out that intelligence is a 80 per cent of heredity and environment of 20 percent. For example, Johann Sebastian Bach belonged to a race in which 57 men, it is assumed that women were not counted, only six had no connection whatsoever with the music.

But the thing is not so clear.
It has shown that the intelligence quotient (IQ) of children adopted by parents with a socially privileged, and with some socio-professional category, is higher than those adopted children in an environment less favored.

It has also been observed that children of parents with higher education have an IQ higher than those whose parents only have studies below. But it is very difficult to know what percentage of hereditary and how much there is for genetic.

Can not establish whether the parents who conducted the studies were conducted because genetically smarter, or just any additional means to carry them out. Nor can we ensure that the IQ of children adopted in a more favored to be higher due to the influence of the environment; inheritance of their biological parents too.