(12-05-2015, 11:02 AM)Valence Wrote: You are sure that say, a chihuahua can reproduce and produce fertile offspring with a mastiff or something similar?
it's got nothing to do with the physical difficulties of copulation, or the outward physical difficulties of carrying offspring to term and everything to do with how the egg and sperm interact and what happens to the offspring genetically. Species identification is actually a fair amount more complicated than this, for example with identifying dinosaur species, or bacteria and things that don't reproduce sexually.
that being said, the 'produce fertile offspring' rule is still sufficient as a condition, just not necessary.
RP scrub incoming 