In a few science fiction series (the Star Trek franchise being
the most notable), humans can mate with extra-terrestrial
species and produce healthy children. This is, of course,
absolutely ridiculous; species are defined by their inability to
mate and produce fertile offspring with other species. Even
taking into account the possibility of panspermia, a human would
have more in common genetically with a daylily than with an
extra-terrestrial. Cross-species mating in Star Trek In the Star
Trek universe, Humans, Klingons, Vulcans, Romulans, and
Cardassians are all cousins whose ancestors were deliberately
sown across the galaxy, and can interbreed just as lions and
tigers (or dogs and wolves) can on Earth, despite massive
physiological (Klingons have two hearts) or biochemical (Vulcans
have copper-based blood) differences. Because of Hodgkin's Law,
not only Trek species but entire Trek cultures developed along
similar paths. Notable products of cross-species matings
include: - Deanna Troi - B'Elanna Torres - A