The sons of fertile, sneaky fathers do share these paternal traits, while sons of attractive fathers are equally appealing, but have similarly impoverished ejaculate.

ECONOMIST: Males can take many routes to reproductive success

There are no fully reliable, up-to-date data on such relevant factors as the age of victims, the rate of their hormonal contraceptive use and what percentage of rapists ejaculate in their victims, researchers say.

WSJ: Pregnancies From Rape Prove Tough to Count

It has been known for years that in a range of animals from insects to birds the males increase the quality and quantity of the sperm they ejaculate when those sperm are likely to find themselves in competition with sperm from another male.

ECONOMIST: Sex: Twin peaks | The