Doc_gnosis

Without first defining the scope of the word "gender" we will forever slide down a point counter-point semantic road to existentialist hell. If we are speaking of chromosomal at birth presentation of biological function and anatomy, well, then its a bell curve. If we are instead talking about a complex social construct that includes at birth biology, developing brain and mental preferences on association identity, sexual preferences, then we are talking about a 5th dimentional bell curve of which we haven't fully studied or identified all the subtexts and nuances to choose from.

The question is problematic in its scope. Let's consider the 5 alpha reductase mutation
It allows an at birth chromosomal male to appear as a biological female at birth through puberty. But once puberty begins the anatomy shifts and the person changes into a male. This natural transgender transformation shows just one example of how we cannot assume only 2 genders exist, but must instead be open to the expression of both biological and preferential identities of everyone.

Then I challenge you to seek out the Guavedoche of the Dominican Republic and read up on a 5alpha reductase mutation that causes at birth girls to transform into boys at puberty.

Okay from your statement it is clear you don't have enough information to make sense of how complex cellular reproduction and asexual reproduction occur in nature. There are multi-cellular organisms that can reproduce both sexually AND asexually via budding, cloning, and species of animals that can literally change sexes in adulthood. Your statement that only male and female gamete reproduction is all that exists in nature is just incorrect.