Cryptic Female Choice

One of the reasons why large mammals are shrinking is because smaller beings need less and are more resilient. In the light of threatening climate change the small have a greater chance at survival, which from an evolutionary perspective, makes smallness an attractive feature. People however mostly ignore this trend. We get bigger despite environmental signals telling us to get small. One of the reasons is that human females feel more attracted to tall males.

Ever since Darwin the dominant narrative on sexual selection is that it is the result of competition between males for sexual access to receptive females, after which copulation inevitably leads to fertilization of the female’s eggs. Tall males have more sex because they often win the competition, and therefore they have more children resulting in a taller average human species. But there are several species of animals that show us that it doesn’t have to be that way. In fact, the act of copulation itself seldomly leads to fertilization: cryptic female choice does. Events within the female body that take place after genitalic coupling decide if fertilization happens. Women have a whole range of instruments to disrupt fertilization, including the lack of sperm transport to fertilization sites, discharge or digestion of current male’s sperm or those of previous or subsequent mates, lack of oviposition, rejection or removal of mating plugs, selective use of stored sperm, and lack of sperm activation. Some of these cryptic choices are available to humans as well. Since the drivers behind cryptic female choice are mostly unknown we can ask the question if current environmental challenges are not already affecting female choice. Perhaps the current infertility crisis is as much a result of unwise partner choice denounced by cryptic female choice as it is of poor sperm count. Even if the mind, manipulated by cultural factors, prefers tallness, the body connected to direct biological signals, might choose small.