Why are there only 2 genders?

Answer 1

GENDER IN HUMANS AND OTHER MAMMALS

There are only two genders becasue God made it that way. Besides, it would be so hard to design a body that accommodated many different genders.

Organisms that have only 2 natural gender selections tend to have much more variation in their genes, which allows them to evolve quicker than organisms that don't, resulting in an improved chance of survival and therefore better chance at reproduction. This becomes less relevant the less complex an organism becomes, like bacteria, which can simply divide and doesn't require another "female" partner to do so.

GENDER IN FISH

Clown fish change genders in their lifetime, but either evolution or god designed it like that.

Also some fish function opposite of expected gender norms, for example, the male sea horse gets pregnant, not the female.

GENDER IN BOTANY

In plants, dandelions get by without exchanging pollen - they are self-fertile.

But ferns have this curious intermediate phase of a prothallus, which surprisingly in turn produces a mobilesperm which then mates etc. Amazing for a 'lower plant'.

GENDER IN SPOKEN AND WRITTEN LANGUAGE

In language, however, there are Three Genders: Masculine, Feminine and Neuter. Many languages such as Latin and Russian divide the nouns into these categories.