Risky sex... among Nile lechwe

According to a recent article in The Economist, the Nile lechwe (an endangered antelope) engages in risky sex--at least the female does. And, no, it's nothing kinky. But researchers have found that as the mothers age, they have a higher percentage of sons. Scientists have not figured out the mechanism behind this, but it is more clear cut evidence of how deeply sexual selection principles are hard-wired into us (including humans). In this case, the sexual shift appears to be a classic example of risk/reward. Almost all females reproduce, so having daughters is a good way to ensure genetic success. Sons are riskier. Only the more successful will mate, but they have the chance to pass along their genes to many more offspring. As female lechwe near the end of their lives, it appears that they are more willing to roll the dice on males, even though male births are also three times more likely to kill them. Apparently, once a female lechwe has neared the end of her ability to breed, she is willing to pay the ultimate price in an attempt to pass along her genes to a greater number of offspring.