Gender is an ancient term; predating biological sex by many millenia. (It literally means "presumed sex").
This is nonsense.
First of all, gender' is a word in English. There are many other languages, and many have only one word for the quality of being male of female.
It has never meant "presumed sex". It's from the Anglo-Norman and Middle French gendre (Anglo-Norman and Middle French, French genre ) kind, sort (c1125 in Old French), sex, quality of being male or female (second half of the 12th cent),
It was expanded to mean the grammatical class of words in some languages - masculine, feminine and neuter (e.g. Latin, German, Old English), masculine and feminine in many families of languages (Celtic languages, Latin-based languages).
In fact our understanding of what makes people "biologically" male or female is constantly developing.
This too is nonsense. There are only two sexes in mammalian species, of which Homo sapiens, humans, is one.