Infanticide: Why Nature is Okay With It

In any court of law, if a person is found guilty of intentionally killing a baby, you could bet some smart money that they are not going to get a light sentence. That's because for humans, infanticide is NOT "okay." However, nature regards this deplorable action very differently, and researchers want to know why.

Numerous field studies and behavioral observations have revealed that infanticide is common among many mammalian species including lions, lemurs, apes, and even mice. Interestingly, even in communal species, such as chimpanzees, the baby-killer is not punished for his actions. He sometimes even benefits from it.

A leading theory as to why this happens argues that males kill infants sired by other males to free up females to have their own offspring. This ensures that their own genes make it to later generations.

Now, a study recently published in the journal Science details how researchers set out to confirm or debunk this disturbing theory.

In an analysis of behavioral data on over 200 species, researchers not only found that infanticide was beneficial for dominant males, but that it was also likely an evolutionary adaptation that even great apes and early humans took on.

"Males don't manage to stay dominant for very long, so when they can mate with the females, they need to do it as quickly as possible," study author Elise Huchard explained to New Scientist.

She explained that "it's not in their interest to wait for the females to finish rearing infants," so they often will slaughter babies that aren't theirs to free up potential mates that will accept their dominance.

In a close look at evolutionary trees, Huchard and her colleagues determined that monogamy - as seen in bonobos, orangutans, and humans - likely developed to prevent infanticide.

However, even for species that didn't take this route, females adapted a smart defense to having their children murdered: promiscuity.

With females having numerous partners during the course of a mating season, an alpha male can become confused, unsure of whose kids are his. In this way, he may not murder any children for fear of killing his own lineage.