Mating Strategies of Males and Females

A vivid demonstration of this difference can be seen by looking up the record number of children sired by a human female versus a male. If you were to guess the maximum number of children that a woman could produce in a lifetime, you’d probably say around fifteen. Guess again. The Guinness Book of World Records gives the “official” record number of children for a woman as sixty-nine, produced by an eighteenth century Russian peasant. In twenty-seven pregnancies between 1725 and 1745, sh...

 Postmating Competition

Sexual selection doesn’t end with the sex act itself: males can continue to compete even after mating. In many species, females mate with more than one male over a short period of time. After a male inseminates a female, how can he prevent other males from fertilizing her and stealing his paternity? This postmating competition has produced some of the most intriguing features built by sexual selection. Sometimes a male hangs around after mating, guarding his female against other suitors. Wh...

 The Wonder of the Fertilized Egg

The opening cast members of the baby-making play are simply a sperm and an egg and a saucy Marvin Gaye song. Once these two cells are joined, they begin producing lots of cells in a small space. The human embryo soon looks like a tiny mulberry. (Indeed, one early development stage is called the morula, Latin for mulberry.) Your mulberry’s first decision is practical: It has to decide what part becomes baby’s body and what part becomes baby’s shelter. This happens quickly. Certain cel...

 A Bizarre Genetic Parasite

Another insect, a scale insect, has an even more bizarre genetic parasite. When its eggs are fertilized. sometimes more than one sperm penetrates the egg. If this happens, one of the sperm fuses with the egg's nucleus in the normal way; the spare sperm hang around and begin dividing as the egg divides. When the creature matures, the parasitic sperm cells eat out its gonads and replace them with themselves. So the insect produces sperm or eggs that are barely related to itself, an astonishing ...

 The Flow of Semen Every Sixty Seconds

Humanity pumps 53.4 billion liters of bloodper minute, but that red river is not surprising; it must flow to sustain life.  At the same time, humanity's male organs eject forty-three tons of semen, and the point is that though each ejaculation is also an ordinary physiological act, for the individual it is irregular, intimate, not overly frequent, and not even necessary. Besides, there are millions of old people, children, voluntary and involuntary celibates, sick people, and so forth. And y...