DesiPundit

High fertility males (who had more fast swimming, normal spermatozoa) had significantly more male offspring. So, in effect, super-males will have more male offspring, who will go on to increase their fertility, and therefore will have greater reproductive success. Low fertility males however, will have female offspring, and therefore benefit by not inheriting lower reproductive quality from their fathers.

Sunil points towards a fascinating new study which apparently proves that stronger males produce more male babies. I guess the Y chromosome is not completely useless. Just for the record, the study was conducted in Red Deer.