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Sexually transmitted infections and monogamy

A unique mathematical study out of Queen’s University has shown individuals are more likely to enter into a monogamous relationship when the result of infection from a sexually transmitted infection (STI) is death as opposed to sterility.

David McLeod

The mathematical study conducted by PhD candidate David McLeod (Mathematics and Statistics) represents the first time a mathematical analysis has been used to determine how STIs might influence monogamy’s evolution.

“Imagine an invisible STI that causes sterility,” explains Mr. McLeod. “You might pair up with a partner with this disease without knowing it, only to find out that the two of you can't produce offspring. You might not catch the STI yourself, but your genes are still out of the gene pool. In this situation, being monogamous disadvantages even healthy individuals.

For the other side of the coin, Mr. McLeod modeled STIs causing death.

“Now imagine an STI that causes death. You might hook up with a partner carrying this STI, but the disease will soon carry your mate away. The partnership may have produced few to no offspring, but you are now free. If you didn't catch the disease yourself, you can go find another partner and try again. A monogamous relationship might protect you if you happen to choose an uninfected partner, but even if you're unlucky, you're only out of the game for a short period.”

Mr. McLeod’s researched was recently published in the Proceedings of The Royal Society B: Biological Sciences.