Will sperm from multiple men fight. If not, they'll "drown" in a thick flow of cervical mucus. This dramatic finding has been widely cited yet largely ignored, and there has never been a follow-up study. In the context of sexual reproduction, natural selection is generally thought of as a pre-copulation mechanism. Aeon for Friends Find out more. All contributing lifestyle and collection variables were controlled for in subsequent analyses. This comment has been deleted. In a mating- guarding system, both parties, male and female, are able to directly and indirectly benefit from this. The general set-up is that copulation with a male causes sperm to be held in all three receptacles.