In , two Japanese reproductive biologists, Katsuhiko Hayashi and Mitinori Saitou, made an announcement in the journal Nature that read like a science-fiction novel. The eggs, once fertilized, were transferred to the uteruses of female mice, who gave birth to ten pups; some of the pups went on to have babies of their own.
Gametes are the cells, such as eggs and sperm, that are essential for sexual reproduction. The Japanese experiment may change the science of human reproduction.
The first successful in-vitro fertilization, in , made it possible to conceive an embryo outside the body.
Today, approximately two per cent of all babies in the United States are conceived in a lab, through I. Egg cells have become commodities that are harvested, bought, donated, and preserved. But egg cells, some of the most complex cells in the body, and large enough to be visible to the naked eye, are difficult to obtain; as a woman ages, their number and quality decline.
A hundred years ago, many Americans died in their mid-fifties. Today, we can expect to live into our seventies and eighties. In the U. Biologists have theories, none of them conclusive, about why women have such a sharp decline in fertility at midlife, and why ovaries age at least twice as fast as the other organs in the body. Deena Emera, an evolutionary geneticist and the author of a forthcoming book about evolution and the female body, told me that the vast majority of female mammals, including chimpanzees, maintain the ability to get pregnant for most of their lives.
