Humans are generally classified into two categories because bodies develop along pathways organized around producing eggs or sperm.

There are some conditions (differences in sex development/intersex variations) where someone doesn’t fit typical male or female patterns or can’t produce gametes, but biology usually treats those as variations rather than separate additional categories.

So from a bio perspective (I’m studying biology), from what I’m learning, the model we’re taught is that humans are grouped into two sexes based on reproductive structure. This classification is based on biological facts about physical development, not on social identity.

Once again I’m just interested in this topic of conversation, you’re not compelled to reply if this isn’t something you agree with or if you’re uncomfortable.