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. In the U.S., as in many other countries, women give birth for the first time at older ages than they did several decades ago, but the age at which women lose their fertility has not budged: by forty-five, a person’s chances of having a pregnancy without assisted reproductive technology are exceedingly low.īiologists 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. Today, we can expect to live into our seventies and eighties. He predicted that in the next twenty to forty years sex will no longer be the method by which most people make babies (“among humans with good health coverage,” he qualified).Ī hundred years ago, many Americans died in their mid-fifties.
GERM ARTOON SKIN
“If ripe human eggs could be derived from a person’s skin cells, it would avoid most of the cost, almost all of the discomfort, and all of the risk of IVF,” the Stanford bioethicist Henry Greely wrote in his 2016 book, “The End of Sex and the Future of Human Reproduction,” addressing new techniques to make stem cells which had won the Nobel Prize in 2012. 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. Egg cells have become commodities that are harvested, bought, donated, and preserved. market at more than twenty-three billion dollars. Today, approximately two per cent of all babies in the United States are conceived in a lab, through I.V.F.-last year, analysts valued the global I.V.F. The first successful in-vitro fertilization, in 1978, made it possible to conceive an embryo outside the body. The Japanese experiment may change the science of human reproduction. The mice that had descended from the lab-made egg cells were described as “grossly normal.” With their experiment, Hayashi and Saitou provided the first proof that what’s known as in-vitro gametogenesis, or I.V.G.-the production of gametes outside the body, beginning with nonreproductive cells-was possible in mammals. Gametes are the cells, such as eggs and sperm, that are essential for sexual reproduction. 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.
The researchers had taken skin cells from the tip of a mouse’s tail, reprogrammed them into stem cells, and then turned those stem cells into egg cells. In 2016, two Japanese reproductive biologists, Katsuhiko Hayashi and Mitinori Saitou, made an announcement in the journal Nature that read like a science-fiction novel.
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