> If not your genes, what else would determine why you have eyes in about the same place in your head as every other human?

Theoretically, it could be second or much higher order effects that result from genes. It could be a combination of complex factors - the environment in the womb, nutrition, behavior by the mother, etc. - that eventually trace back to DNA.

Also, is it literally true that DNA is the only thing that's consistent (in these respects) between all generations of Homo sapiens?