Man: I'm in a polyam, I'm going in last. How do I ensure the kids will bear my genes?
Nature: I have a few tricks up my sleeve. 😝
References
Baker, R. R. and Bellis, M. A. (1995). Human sperm competition: Copulation, Masturbation, and Infidelity. Chapman and Hall, London.
Gallup, G. G., Burch, R. L., Zappieri, M. L., Parvez, R., Stockwell, M. and Davis, J. A. (2003). The human penis as a semen displacement device. Evolution and Human Behavior, 24, 277–289.
Gallup GG, Burch RL. Semen Displacement as a Sperm Competition Strategy in Humans. Evolutionary Psychology. January 2004. doi:10.1177/147470490400200105