Oops, just because it's genetic doesn't mean there is a gene, or are genes, directly FOR it. It's more that the way our bodies and brains are shaped in embryology, which IS directly genetic, makes us be the way we are, including having the ability to be other than the way we were made.
Other animals don't have it so lucky.

But then again, as the old song says,

(If I were a duck and I lived on the water
I'd swim 'round the pond and go Quack
I'd swim just as far as I wanted to go
And then I would turn and swim back

If I were a cow and I had a fine pasture,
I'd eat lots of grass and go Moo
And then I'd go home to the barn to be milked
And give a whole gallon or two...)

If I were a squirrel and I lived in an oak tree
I'd eat lots of nuts and grow fat
Then lie on the limb of the tree in the sun
O what could be nicer than that?