From Carl Zimmer at the New York Times:
Dr. Lukas and Dr. Huchard then looked at how infanticide might have evolved over the past 160 million years of mammal evolution. “When we started, we weren’t sure if infanticide was present in some ancestral mammal and is just more pronounced in some species and is lost in other species,” said Dr. Lukas. “Or maybe it just evolved in those species where the conditions were right.”
Their research supports the second scenario. The common ancestor of living mammals did not practice infanticide: The behavior evolved later and independently in a number of separate animal lineages.
Dr. Lukas and Dr. Huchard found that the species that evolved infanticide had a few things in common. For instance, the females tended to give birth year-round, rather than at just one time of the year. Another key factor was that males and females lived in groups where females greatly outnumber males.
Now, what is really interesting is that Zimmer avoids saying “And that explains why some men murder their stepkids,” choosing rather:
Among the mammal species that Dr. Lukas and Dr. Huchard didn’t include in their study was our own. Dr. Lukas said the cultural diversity of humans means it is hard to make blanket statements about them. “For many social behaviors, it’s very difficult to define a human universal,” said Dr. Lukas.
That’s not to say that adults never harm — or even kill — children. But Dr. Hrdy argued that the infanticide she documented in langurs — in which males stalked babies for days —was fundamentally different from what happens in our own species.
“A male would have to pull out a butcher knife and stab the baby, but that’s not what you’re seeing,” said Dr. Hrdy. “I don’t think langur infanticide tells us much. I think it’s a very different phenomenon.”
Good for her. It is a different phenomenon in humans.
But, actually, we’ve had a research team at McMaster University in Hamilton (Ontario, Canada) Martin Daly and Margo Wilson (deceased 2009) claiming for decades that this explanation applies to humans. Such research is often protected from falsification by political correctness.
That is, the question skeptics aren’t usually allowed to raise is, In a typical developed human civilization, who just kills some other guy’s kids anyway?
“Hey, I just knifed my new bride’s kid with her ex-husband. Wanna join me for a beer?”
Obviously, it has to be someone who doesn’t much care what most people would think or what the law says. And if the human race supposedly evolved to behave that way, why is it considered so abnormal that in most places today it incurs the death penalty or life imprisonment?
Of course, the ultra-Darwinian will say that natural selection naturally selected humans to put in place such measures.
But given that most North Americans (just for example) disrespect Darwin anyway, another explanation worth considering might be this: Most men who kill other guys’ children (who happen to be living with them) have a history of conflict with social norms and the law, and might be clinical sociopaths.
There were probably few periods in human history when their behaviour was considered normal and understandable, but some periods where it was not followed up, in the absence of law enforcement.
So Hrdy is wise not to apply the thesis to humans beings. As she says, it is a very different phenomenon.
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