>>1658730Incoming wall of text [1/3]
Here are some of my two cents on the topic:
This is also a question I have thought about a bit. The common approach to answering this is to look the definition of being a man from a prospective perspective instead of a retrospective one. Or put differently, how did the phenomenon of "man", and "woman" for that matter, arise from a world that was devoid of both in the first place?
Biologically, the first lifeforms on earth, simple single celled organisms, were asexual and reproduced by splitting in two halves. While functional it doesn't allow for the transfer of beneficial genes to the rest of the population(let's ignore viral transmigration for simplicity for now), if a new cell has an advantageous mutation, only its direct descendants will have that mutation and if they are superior enough will have to replace the rest of the population over time.
At some point some organisms evolved the ability to exchange genetic information. The advantage of this is that a new mutation can be integrated in to the rest of the population without having to replace it, greatly increasing the adaptive responsiveness of the whole population, giving it a significant survival advantage over asexual reproduction. An example of this would be snails which are unisex but still mate sexually.
This agendered sexual reproduction allowed for the rise of sexual dimorphism, or different phenotypical expression within the same species. This is where the first distinction between males and females as we like to think of it arose. Why develop different expressions of the same base genetic code? Specialization. Carrying around reproductive organs requires energy just to maintain them and usually this is not a trivial amount. If some members of the species can forgo this energy burden, they can take on other roles or develop traits which would be too costly otherwise.
