A brief essay in a recent issue of New Scientist magazine called "Infanticide drives female promiscuity and big balls" caught my eye. (The title for the print edition of this essay is "Big balls a sign of mammal infanticide.") The essay is a summary of a research paper published in Science magazine by researchers Dieter Lukas and Elise Huchard with the less flashy title, "The evolution of infanticide by males in mammalian societies."
The original paper is only available to subscribers and was widely reviewed in popular media, including Carl Zimmer's essay in The New York Times called "Unraveling Why Some Mammals Kill Off Infants." Mr. Zimmer writes, "The authors of the new study, Dieter Lukas and Elise Huchard, started by plowing through the scientific literature, looking for evidence of infanticide in a variety of mammalian species. The researchers ended up with data on 260 species, and in 119 of them - over 45 percent - males had been observed killing unrelated young animals." Furthermore, infanticide evolved because "Killing the offspring of other males can free up females for reproduction and widen the window of opportunity for new males, leading to more offspring for them." Forty years ago renowned researcher Sarah Blaffer Hrdy put forth the same idea based on her research on Hanuman langurs in India.