While in high school I took a year-long anatomy and physiology course and one idea stuck with me when learning about the reproductive system. My teacher told us that if men wear briefs they are more likely to have a child who is female, while if they wear boxers their child will most likely be male. She said this was because briefs caused the sperm to be warmer (resulting in females) while boxers allowed for cooler sperm (resulting in males). I always considered this idea to be true until this semester when we examined the reproductive system in closer detail. It turns out that certain species of reptiles use environmental sex determination (ESD) based on environmental temperatures to determine the sex of their offspring (Pezaro et al., 2016). Therefore, since human sex determination mechanisms are based solely on genetics (i.e. X and Y chromosomes) and reptiles sex determination mechanisms are based on environmental factors how could this be true? Well, there is a theory circulating that due to climate change and rising temperatures the gender ratio of humans will change as more females are likely to be born due to heat causing stress on sperm and resulting in female characteristics (MacDonald, 2017). Though this theory is currently just speculation and there is no substantial research to support this theory, it could be an interesting future study.
Although the type of underwear men wear may not affect the gender of their offspring it does affect the sperm count and other factors of sperm in relation to reproduction. One study conducted on 656 males found that men who wore boxers were more likely to have higher sperm count and concentration and lower FSH levels in comparison to men who did not (Mínguez-Alarcón et al., 2018). Tighter underwear is the main culprit for higher scrotal temperatures resulting in poorer quality semen. Though temperature may not be a factor in sex determination in humans, it does affect the quality and amount of semen produced making it an important factor to consider when trying to reproduce.
References
MacDonald, J. (2017, March 9). Climate and gender: Too few males? JSTOR
Daily. https://daily.jstor.org/climate-gender-males/
Mínguez-Alarcón, L., Gaskins, A. J., Chiu, Y., Messerlian, C., Williams, P. L., Ford, J. B., Souter,
I., Hauser, R., & Chavarro, J. E. (2018). Type of underwear worn and markers of testicular function among men attending a fertility center. Human Reproduction, 33(9), 1749-1756. https://doi.org/10.1093/humrep/dey259
Pezaro, N., Doody, J. S., & Thompson, M. B. (2016). The ecology and evolution of temperature-
dependent reaction norms for sex determination in reptiles: A mechanistic conceptual model. Biological Reviews, 92(3), 1348-1364. https://doi.org/10.1111/brv.12285
It’s interesting to me that people are trying to study what factors affect gender especially because this topic feels like a form of eugenics, where people try to engineer specific traits or try to increase the chances of a child having certain characteristics.
ReplyDeleteThere are actually quite a few different methods that have been developed in sex selection. Gender-selection kits like Gen Select and Smart Stork are based on when intercourse occurs. There are also more “natural” techniques such as changing diet prior to conception (Rai, 2018). However there does not seem to be much science backing these techniques. These could promote gender biases and inequalities and seem to be big marketing schemes. I would love to see more data on how any of these factors (intercourse timing or diet) can really change how our physiology or determine what sex our future children would be.
References
Rai, P., Ganguli, A., Balachandran, S., Gupta, R., & Neogi, S. B. (2018). Global sex selection techniques for family planning: a narrative review. Journal of reproductive and infant psychology, 36(5), 548–560. https://doi.org/10.1080/02646838.2018.1508871