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...

 Testosterone's Effect on Memory

Like many other areas of development, memory generally matures more rapidly in girls than boys. Beginning in the womb, female fetuses are known to habituate to auditory stimuli about two weeks earlier than males. After birth, they are more advanced at visual habituation. Toward the end of the first year, girls are about a month ahead in tests of short-term, explicit memory, like remembering, after a few seconds' distraction, where they just saw a toy being hidden. Girls also outperform boys o...