Total hypothesis by me below. I do have to admit that I do have a gene-centric bias as influenced by the arguments in The Selfish Gene. Not all of these bullets come from that book, but are influenced by it.

• Genes are replicating entities whose sole purpose is to make copies of themselves.

• Genes use multiple tactics [I apologize for personifying them, it's just handy to employ the language] to outcompete other genes in a resource-constricted environment. Some of these tactics include creating bodies to carry them, and combining with other genes, etc.

• As far as mammals are concerned, we typically have a female part of the species that makes large, immobile, nutritive eggs, and a male part of the species that makes multiple, mobile, non-nutritive sperm.

• Mammals create their sperm and eggs through recombination of each copy of the DNA they inherited from their parents.

• There are multiple regions of the brain, each developed by natural selection

• There is a region of the brain where our consciousness is "located." Whether that consciousness only resides on one section, a few, or is the result of the interplay of them all is another debate entirely. For now, I will only say that we have consciousness, that it is a function of our brain, which again is the result of natural selection.

• Animal bodies are driven by natural selection. The body is not the true unit of selection, but rather the genetic variations and recombinations that make that body. These genes' ability to make a body for the purpose of replicating themselves is how they are selected.

• There has been observed in the wild, and described in evolutionary terms, certain runaway feedback loops in mate attraction. Specifically, the story of the peacock's plumage and other exaggerated, and seemingly-unnecessary bodyparts on other animals, is one of these stories. There is a balance that peacocks must strike between attracting a mate and not getting eaten before they can. Large tails inhibit their ability to avoid predation, but the off-set occurs with how often they get to mate. Peacock genes which produce very large peacock tails tend to replicate themselves more genes that make small peacock tails, even though those peacocks may not get eaten as often.

Okay, let me synthesize those bullets.

Genes control your body, what you look like. Genes control what you are attracted to. Genes recombine as well.

As far as being attracted to one sex or another, genes for being attracted to males may only exist in female genes, and genes for being attracted to females may only exist in male genes. However, there may exist a mechanism where those genes for attraction get flipped in the recombination process for making eggs and sperm. Or perhaps it could be the result of a mutation. This could account for both the existence of homosexuality, and why it is in a minority of cases.

As far as identifying as one gender or another, I'd reference my bullets on consciousness, because my gut tends to trend that direction -- that genes control the development of the brain hardware, and consciousness and the concept of identity and social interaction might be manifestations of firmware or software.

I think that genes still are the dominating force in self-identity. Most people just "feel" it rather than "learn" it.