Breaking Bad Science

Episode 87 - Birth Rates Aren't 50-50

February 27, 2022 Daniel Episode 87
Breaking Bad Science
Episode 87 - Birth Rates Aren't 50-50
Show Notes

We’d love to hear from you (

Look us up on social media 





When my wife was first pregnant with our son, we were desperate to try to figure out the sex. We discovered that people had some of the most interesting theories about what factors would influence this result in the end. Right down to how the deed was done. The reality is, in the simplest form that the male sperm decides the gender and that is produced at a 1:1 ratio. But if that's where the story ends shouldn't birth rates be 50:50 as well?  Join hosts Shanti and Danny as we discuss the idea that maybe they're not? If there is something else going on, what the actual rates are and why might this actually make sense? 


  1. Statista. Resident Population of the United States by Sex and Age as of July 1, 2020. July-2021.
  2. Orzack, S., et. al.; The Human Sex Ratio from Conception to Birth. PNAS. 21-Apr-2015. 112:16 (E2102 - E2111). Doi:
  3. Spears, K., et. al.; Gender, Famine, and the Female Mortality Advantage. World Peace Foundation and Tufts University. Dec-2021.
  4. Song, S.; Does Famine Influence Sex Ratio at Birth? Evidence from the 1959 - 1961 Great Leap Forward Famine in China. Proceedings of the Royal Society of London: Biological Sciences. 22-Jul-2012. 279: 1739 (2883 - 2890). Doi:
  5. Knox, R.; Examining Environmental Factors in Sex Ratio. NPR. 18-Jul-2005.

Support the show