Link to the original study: https://www.pnas.org/doi/10.1073/pnas.2202874119

The data comes from a very specific polulation:

> His data come from a survey begun in Cebu City, in the Philippines, in 1983.

I'm not sure if it can be generalized.

This study used a saliva test for measuring testosterone. From what I read it doesn't appear that they accounted for diet, weight, and sleep all of which have a direct effect on t-levels and will change drastically if a father is active in the care of his newborn. Without good sleep and diet your testosterone could plummet to less than half of your average levels.

For any discussion on testosterone, I highly recommend the Huberman lab episode[1] on the topic. Crazy packed with information.

1: https://open.spotify.com/episode/0KeCWwDkdbEGFBXW0SFtK1?si=O...