Women After All: Sex, Evolution, and the End of Male Supremacy by Melvin Konner

inflates his neck, and makes a series of low booming noises. As he does this, his feathers puff up. When he sits down, the chicks cuddle up to him, often snuggling into his feathers. . . . The chick also picks ticks off its father’s neck and eats them. Yum.
    Meanwhile the errant mom is off to greener sexual pastures. As one (human) mother of five put it to Judson, “I’m coming back as a female cassowary.”
    Cassowaries are the biggest birds with devoted dads and hit-and-run moms but not the only ones. Jacanas, also known as Jesus birds, trot on lily pads and so seem to walk on water, but that’s not their main claim to fame. What they are most known for is that, as in the cassowary, the sex that invests more in the young is the male. Before the female lays her eggs on her chosen lily pad, she collars a male who is bound to take care of them, and that’s the end of her interest. The male? Seduced and abandoned, while the female, twice his size,goes off to mate with another male—as many as four in an hour, thirty in a season. Wham, bam, thank you . . . sir ?
    Only there’s not even that much of a thank-you in this water-lily world, where the females are too busy fighting off rivals and mating here, there, and everywhere to bother with the niceties. Their adversaries? Other females, who are trying to steal their males. By the end of the season they’ve a harem of cute little dads, each slavishly brooding a clutch of eggs, then doting for most of a year over a clump of chicks. But all of the father’s effort won’t necessarily stop the odd menacing female prowler, who can (when the boy-harem’s Amazon queen has her back turned) trot in, cow a pint-sized pa, peck open his eggs, and dispatch his hard-won babes.
    And it isn’t just the brooding. He may have risked his life to draw a snake or alligator away from them, instinctively flopping around as if he had a broken wing, so the not-too-bright predator would forget to eat his little ones. But now he sees a strange female—twice his size, true, but probably less dangerous to him than the reptiles were—and does little or nothing to stop her from doing in the chicks. Why?
    Probably because of what happens next. She displays her (to him) intensely attractive rump, and soon enough he mates with her, fertilizing her eggs. She has won the prize away from the first female. The prize? The sex that invests more in the young. Although she has the upper wing, she is just, as ornithologist Stephen Emlen put it, an egg-making machine. The future dad instinctively starts pulling together a new nest on the lily pad, and in a week or so the once-menacing intruder returns, lays some eggs, and goes off to her next conquest. In due course, the pond is dotted with single-father families.
    Eight species of jacanas circle the globe in tropical zones, and despite some fossils, we don’t understand their origins. It’s likely, though, that they evolved from pair-bonding birds, of which there are some eight thousand species. They, too, tend to have devoted dads butnot single ones, since parents share the burden of raising the young more or less equally. And it is a burden.
    Watch the little perching birds in your eaves or garden. If they have a nest of chicks, they fly off nonstop in tandem—they practically need an air traffic controller at the nest—to bring back food. When they alight on the nest’s edge, they face a bevy of gaping mouths, often colored and marked in ways that, along with incessant peeping, turn mom and dad into doting slaves. If you’re a parent yourself, this may sound familiar. If not, take a moment to thank those who slaved away to keep you in earthworms and away from dangerous cats. Humans, we’ll see, are largely pair-bonding too, a fate that carries with it a suite of other adaptations under the logic of sexual selection.
    In most pair-bonding birds, the sexes are about the same size, and usually neither has evolved extra weapons or great beauty compared