Quoting some Dawkins on what "a gene for X" means: When a geneticist speaks of a gene "for" red eyes in Drosophilia, [...] he is implicitly saying: there is va

Quoting some Dawkins on what "a gene for X" means: When a geneticist speaks of a gene "for" red eyes in Drosophilia, [...] he is implicitly saying: there is variation in eye colour in the population; other things being equal, a fly with this gene is more likely to have red eyes than a fly without the gene. That is all that we ever mean by a gene "for" red eyes.