Daughter or son, which sex to produce?

Female bighorn sheep with her young.

(c) Peter Neuhaus


The right offspring sex can increase the number of grandchildren. Theory predicts which offspring sex is optimal depending on the mother’s condition, but mothers in natural populations do not behave according to theoretical predictions. We explain the reason for the mismatch and provide more accurate predictions.


Schindler, S., Gaillard, J., Grüning, A., Neuhaus, P., Traill, L., Tuljapurkar, S., & Coulson, T. (2015). Sex‐specific demography and generalization of the Trivers–Willard theory Nature, 526, 249–252DOI: 10.1038/nature14968