Well, I wouldn’t say it’s been conclusively proven, but statistically there is a definant relationship to heredity.
alcoholism.about.com/od/genetics/a/blacer060508.htm
This means that genes
could be altered by actions… This would mean that Darwin’s theory is lacking because he failed to take into account that necessity and desire and even sin in humans can play a role in evolution. Instead he based it all on sex and survival.
It could be that the giraffes neck grew so long because it was addicted to a certain type of leaf, and that addiction was passed down from generation to generation genetically. They loved that leaf so much that their body actually changed genetically through time out of necessity rather than through only sex and survival. So I think genes become altered through addiction (sin), as well as desire. The two are related after all.

this is opposed to the idea that “natural selection” is the only factor in gene mutation as Darwin suggested.