You are confusing gender with sex and sexuality. They are all different things. First sex is what genital you are born with. As you pointed out even this is not binary as there can be more then two. Gender is more psychological/emotional. Gender is more about what you feel then what you have. Sexuality is about who you are attracted to.

@Ldox Not at all confused. My use of the terms* is as found in Anthropology and Biology. They are quite precise, but in actual use it us acknowledged that there is some overlap. For example: you can have a baby born XY (gender), but whose external morphology is that of a female (sex), but whose behavior will later assume "male" character role. And of course, this is merely an example of all the numerous permutations that can occur.

Should have also brought up the topic of Chimerism, where a person can be partly XX and XY genetically.

*Spell Check converted my "Sex" to "Sexuality", I will fix that. It does cause confusion

@Reignmond lol The funny thing is babies are not just xx or xy there are also xxy and xyy as well as more possible combinations. However gender in this instance is the sociological usage. It is fun chatting with you on this subject as I am learning quit a bit in the process. Just so you are aware though Gender is not used in biology to describe the chromosome distinction of a person. At least not according to this. I did have to look it up as I do not remember the term ever being used in my biology classes, however I did not major in biology. [biology-online.org] Either way this all shows that it is not binary as other options do exist.

@Ldox
I did allude to Jacob's and Klinefelter's syndromes (and their similars) in my original post. I would still contend that since it is not an accepted process to typify an organism by its genetic deformities, it is basically binary, which is then modified by the environment, even before birth.

It's all down to semantics. I understand sex to be biology and gender to be identity, plus all of the nonsense that we assign to biology that isn't directly related to what's in our pants.

Male and female are well defined, anatomically tangible constructs. They're understood the world over, even if different languages have different words for them. While not strictly binary either, generally speaking (in mammals) male = has penis and female = has vagina. In other species, the reproductive anatomy may vary. In flowering plants, you have the stamen as the male sexual organ and the gynoecium as the female.

Gender is a social construct with diverse cultural influences, and almost exclusively applied to humans. You wouldn't call a female horse a woman. You wouldn't call a male fish a man. To be a woman in Saudi Arabia is a very different role to being a woman in the West. We even accept multiple gender roles beyond the generally accepted two, without anyone even noticing. Boy and girl are distinct from man and woman, with all four having different, gendered roles in society.

XX and XY? Massive red herrings. It's been long established that the Y chromosome is only one factor in determining male development patterns. There are conditions such as AIS, where the body isn't responsive to male hormones, making genetic XY individuals exhibit female development patterns. But above all, the only function of sexual genetics is to produce hormones, and it's hormones that do all of the work. These hormone levels can be very easily blocked or supplemented with medication. So someone with (medicated) high estrogen and low testosterone is male purely because they're XY? That's like saying the Elvis cassette that you recorded The Rolling Stones over is still an Elvis cassette.

"Gender is binary," with authority! In 2018. Lol. ?