Men

Adult human males. This common definition, however, is insufficient for feminist analysis.

So...

Men

• A class of people created by gender divisions, which gendered ideology necessarily conflates with the biological fact of being male.

• The people who belong to that category:
  • Male people, automatically enlisted in the gender class because of their biological characteristics.
  • Particularly, adult male people (as opposed to boys).
  • Transgendered people, who choose to enter into the gender category.

• See also: Man.

Men in SF

Like women, men in SF are apt to be non-human. Male aliens, or neuter aliens -- aliens who lack the marked characteristics commonly associated with women in popular gendered ideology -- can still be called "men" if they are even remotely anthropomorphised.

It's that whole mankind syndrome thing.

Thus: little green men, bogeymen, werewolves (the "were" means "man"), Cybermen, etc.

When the default for humanity is male, then it's easy to project that default onto imaginary species as well.