J. Brad Hicks compares Sarah Hrdy’s discoveries about infanticide to the forbidden knowledge of Arthur Machen’s horror classic, The Great God Pan:
So she quietly continued her study, working behind the scenes with other researchers while she directed her own studies towards less controversial animals, such as insects. Eventually she discovered something that appalled even her with its simplicity. Not only do mothers sometimes kill their own children, they are almost never insane when they do so. On the contrary, for a mother to murder her own child is an evolutionary adaptation without which our species would not have survived some of the environmental and social disasters of the past.What’s more, the actual reasoning behind this is so simple that a straightforward simple equation in four variables is sufficient to provide a reliable estimate of the probability that any particular mother will murder any particular infant: the age of the mother, whether or not this child is the gender that the mother wanted (which, itself, turns out to be easily and universally predicted based on only two variables, the mother’s social status and the predicted reliability of the food supply), the child’s birth weight (and to a lesser extent other indicators of long-term viability), and her estimate of whether or not attempting to nurture this particular child will only get both her and the child killed.
When she took her early estimates for this equation to the 1990 conference, she discovered that epidemiologists studying SIDS, primatologists studying infanticide (following her 1976 tip), historians digging through old records to try to quantify infanticide throughout the ages, criminologists and social psychologists trying to come up with statistical models to predict mother-on-child infanticide, and anthropologists trying to statistically analyze what variables are most consistent with cultures that have high versus low rates of infanticide, had all independently discovered the same equation.
And from her viewpoint as an evolutionary biologist, Hrdy demonstrates that any sane, healthy, normal, intelligent mothers who weren’t capable of coldly murdering their own infant children almost certainly had no surviving descendants at all to be our ancestors during some of the species-wide threats that have been demonstrated to have happened from the fossil record and from studies of rates of genetic drift.
Hrdy’s work led another researcher to the conclusion that 75 percent of SIDS cases were infanticides.