A recent study published in the Proceedings of the National Academy of Sciences suggests men's testosterone levels fluctuate when they have children.
The study measured the testosterone levels of 600 participants when they were 21-years-old and then again when they were 25. Men with high testosterone levels were more likely to find a mate and father a child. After having a child, though, their testosterone levels dropped significantly. And the more time these fathers spent with their children, the lower their testosterone level was. Single men, however, had a steady level of testosterone after four years.
The researchers suggest this physiological reaction is beneficial to the father as he needs to be more nurturing and less aggressive after having a child. Though he may not like the idea of losing some of his testosterone-fueled manhood, these changes may help him become a better father. [Scientific American; Image from AnnaKostyuk/Shutterstock]