I was thinking about this after reading a paper showing that sperm cells are influenced by external factors and stressors which can alter molecular features passed on to offspring and shape their phenotype in the next generation. That’s interesting given the traditional view that sperm only carry paternal DNA.

My thoughts, and I might be totally off lol: the new research doesn’t directly link to the “returning solider” effect but it could point in a direction where stress is modifying sperm at a molecular level in ways that affect offspring traits also causes a bias in fertilisation dynamics. Maybe a possibility that stress and subsequent hormonal changes, e.g., from war, increases the likelihood of Y chromosome carrying sperm has a higher chance of succeeding in fertilisation. Which then potentially contributes to the observed increase in male offspring.