Parasitic manipulation of human sexual behavior
Parasites don't want to kill you. They want to use you.
Toxoplasma gondii (Wikicommons: Ke Hu and John M. Murray)
The Encyclopedia of Sexual Psychology and Behavior has just published my entry on parasitic manipulation of human sexual behavior.
Here is the abstract:
A surprising number of tiny parasites can infiltrate brain tissue and make their current host behave in ways that help them spread to new hosts. Do such parasites exist in humans? We would be ideal vectors, given our complex neural circuitry, our social nature, and our dense populations. In fact, many microbes use our web of personal relationships, notably our sexual relationships, to go from one body to another, and natural selection should favor those that spread to the most bodies.
To increase the rate of spread, selection may act on the host’s behavior. In theory, all sexually transmitted parasites are being selected for the ability to manipulate host behavior. Because their success depends on how often and with whom their current host has sex, even a slight behavioral change may significantly help them spread to other individuals.
The full text can be found here: https://www.researchgate.net/publication/408513206_Parasites_Manipulation_of_Human_Sexual_Behavior
Comments are welcome.
Reference
Frost, P. (2026). Parasites: Manipulation of Human Sexual Behavior. In: Shackelford, T.K. (eds) Encyclopedia of Sexual Psychology and Behavior. Springer, Cham. https://doi.org/10.1007/978-3-031-08956-5_2536-1
After reading your paper, I guess that has been my (lifelong) problem wrt women and my sex life—not enough parasites. 😢
Very interesting.
I found the following quite intriguing: “Indeed, some diseases of old age may be due not to old age itself but to long-present parasites that have nothing to lose anymore. By that stage of life, the host has stopped having sex, at least regularly, and can be harmed without any real loss.” Could you elaborate on this? In what way would such parasites harm hosts that have reached old age? In other words, how would such a change of strategy benefit the parasite and what would it consist of?