Nature pulls off a small miracle each month: Just one egg matures in an ovary and bursts forth to reach the fallopian tubes, ready to be fertilized. Assisted reproduction now makes maturation and fertilization work in the lab as well.
In the beginning, no one really understood how babies were made. Thinkers puzzled for millennia about how life arose from one generation to the next. But not until the 17th century did scientists start to seriously study the question. At that time, the theory of preformation held that minuscule humans already existed, fully formed, in either the mother’s menstrual blood or the father’s semen, depending on whether you were an “ovist” or a “spermist.”
Little changed until two late-19th century scientists, Oskar Hertwig from Germany and Hermann Fol from France, independently conducted experiments on sea urchins, proving conclusively that creating new offspring takes one egg and one sperm.
Despite the early confusion, the ancients were sure about one thing: Reproduction is far from a sure bet. Today, an estimated 15 percent of couples worldwide are unable to conceive a child naturally, leading to feelings of sorrow, loss and a profound sense of inadequacy for many. A century ago, science didn’t have much to offer these couples.