more on the cinderella effect

greying wanderer suggested the other day that a murderous person would prolly stab a stranger with a knife up “to the hilt,” but if he went to stab his brother, he might, at the last second, have a change of heart and only stab the blade in an inch or two.

there might be something to that notion. what he said reminded of something i read a while ago now, around the time i had a couple of posts about the cinderella effect, i.e. that step-parents generally don’t treat their step-kids as well as biological parents do. this makes sense, of course, if you keep inclusive fitness in mind, ’cause step-parents are (usually) not related to their step-kids.

what i read was a really interesting, but depressing (esp. for a chick, i think), article entitled “Some Differential Attributes of Lethal Assaults on Small Children by Stepfathers versus Genetic Fathers.” what the researchers found was that, not only do step-parents kill their step-kids at much greater rates on average than biological parents, but that when they do, it’s usually a more violent, brutal affair. when biological parents do kill their own kids, they tend to do it in a rather clean, almost humane way. and they more often kill themselves as well afterwards.

“Killings of children less than five years of age by stepfathers versus (putative) genetic fathers are compared on the basis of Canadian and British national archives of homicides. In addition to previously reported differences in gross rates, the two categories of killings differed in their attributes. Beatings constituted a relatively large proportion of steppaternal homicides, whereas genetic fathers were relatively likely to shoot or asphyxiate their victims. A substantial proportion of killings by genetic fathers, but almost none of those by stepfathers, were accompanied by suicide and/or uxoricide. These contrasts lend support to the hypothesis that the differential risks incurred by children in different household types reflect the differential parental solicitude that is predictable from an evolutionary model of parental motivation.”

here are some charts.

methods of killing of children under five, canadian study — that first category is “beat”:

methods of killing of children under five, uk study — the categories from left to right are “hit, kick, blunt object,” “shoot,” “suffocate, strangle, exhaust fumes,” and “all other”:

relatedness matters. even — or maybe especially — in the most gruesome scenarios.

so, if you’re a parent, and you’re thinking of re-marrying (or re-shacking-up, altho that’s prolly a bad idea anyway), CHOOSE CAREFULLY.

btw — you would think that it would also make a difference if, say, a child was mixed-race or mixed-something. in such a case, the biological parent would clearly be less genetically related to their child than in a family that was 100% swedish or chinese, for example. not to mention all the cousin-marriage scenarios i’ve been talking about (ad nauseum). you would think, all else being equal (like economic circumstances), that there ought to be less child killing by parents in a place like saudi arabia.

and, that’s all i’m going to write about this subject (for now anyway), ’cause it’s just too d*rn sad.

previously: evo psych in need of a little hbd? and killing kids & step-kids, part ii and the cinderella effect, again… and even plants do it and more plants playing favorites

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