The third condition is parasites. For even if the two previous conditions existed, the organism might still reproduce itself without the inefficiencies of sexual partnership. The fact that sex, in its most primitive manifestations, is asexual and has nothing to do with pleasure offers some confirmation of this idea. And courtship, we know, is a wonderfully frivolous device. Even when the organism manages to see it through successfully, the reward is the preservation of only half its genetic material, as opposed to all of it. Yet introduce the parasite and this inelegant precaution becomes obligatory. For consider the parasite in its ideal form. The perfect parasite would be one which is capable of utterly subordinating the interests of its host to the interests of itself. It would be impervious to the best defenses of the immune system, antibiotics, and Catholic souvenirs. Asexual reproduction would transfer all the susceptibilities of the host to the next generation. It is only in the scrambling of the genetic puzzle which sexual reproduction affords that the irresistible forays of the perfect parasite might be forestalled.