Board Thread:Warhammer 40k General Discussion/@comment-7699236-20130626164907/@comment-32788838-20140213174513

The thing about those animal hybrids is that their species share a genetic heritage recent enough for them to still retain a lot of the things that keep them the same, and even then a majority of hybrids I know of are sterile and incapable of producing further offspring. A human and an eldar vary wildly from one another in great multitudes that would make it maybe impossible for them to even engage in a sexual act. The eldar are entirely alien to us and are most probably biologically incompatible to us in more ways than just creating spawn.

It wouldn't matter about urges if you don't have the right equipment or stamina in order to even engage in procreation, let alone produce a spawn from it. It would be like trying to make a natural, biological spawn between something like a dog and a tree. Disregarding cultural factors, actual intercourse could just be near damn-well impossible as producing a spawn from it if it could happen.