The 1989 book, Heather Has Two Mommies, normalized for my kids the idea that two women could care for a child and create a fine family. The controversy it met with seemed increasingly quaint as research showed that kids like Heather grow up very much like average children, although they are less homophobic.

Even quainter now seems the battle over the first “test-tube baby.” Louise Brown, born in 1978, was hailed in headlines as “Superbabe” and “The Lovely Louise,” but she also met with many negative expectations. Yet in 2010 Robert Edwards shared the Nobel Prize for the work that led to her birth, celebrating with Ms. Brown and her own son. Today five million people conceived in this way walk among us, indistinguishable except in the luck of their existence.

But suppose these two lines of research could be joined. Suppose Heather had two biological mothers—because one of their eggs was fertilized with the DNA  of the other. Since the offspring of such a union could have only X chromosomes, the headline “Superbabe” might take on a new meaning, although “Supergirl” or “Superwoman” would be better. How close are we?

Last year Britain passed a law that allows a baby to have three biological parents: a father, a mother, and a mitochondrial mother. In rare cases Hannah (say) has a rare disease of mitochondria—our cells’ energy stations—that she will pass down to her daughters. To help Hannah and her partner avoid that, Marian volunteers her mitochondria. Or more exactly, Marian volunteers an egg, which has the main DNA from its nucleus—her biological essence—replaced by Hannah’s DNA. Only the mitochondria are still Marian’s. And the baby will still be half Jack or Joe.

This is not the future, it is happening today. Now imagine transferring the second mom’s DNA into a sperm, and using that to fertilize the first mom’s egg. Science fiction? Slightly, but there is something easier on the horizon. Various laboratories are reprogramming adult cells to make what are called germ cells, which in turn become eggs or sperm.

So now Heather’s two mommies—Rachel, say, and Rebecca—have a choice before she is conceived. Instead of having Rachel become pregnant with a man’s sperm, and then maybe giving Rebecca her own turn at pregnancy, Rachel can (theoretically) have some of her cells reprogrammed into germ cells—creating, in effect, female sperm. After that, we’re only talking (in technical terms) about the same sort of in vitro fertilization that has already given a start in life to millions.

There is a slight hitch, although some may see it as an advantage. Since neither Rachel nor Rebecca has a Y chromosome, all their babies will be girls. Heather can be named before she is conceived.

The end of men? Not really, at least not right away. Same-sex couples are a minority, and perhaps only a few of them will choose this method if it becomes available. Why couldn’t men do it too? Well, they could with the same kind of reprogramming, and there are technical reasons to believe it might be easier. They could even have babies of both sexes.

But: they would need a womb. There are limits to surrogacy. Perhaps in the long-term future this obstacle could be overcome, with completely artificial gestation. But that seems much farther away, while in the foreseeable future lesbian couples, or any two women, should be able to have a baby without involving a man. In time, girls would begin to outnumber boys.

Worldwide, this would first correct the imbalance already created in much more questionable ways. There are 85 to 100 million “missing” women, mainly in Asia, a skewing arrived at through differential neglect, gender-biased abortion, and infanticide. The resulting excess of men may lead to more crime, social unrest, and often-unruly male sexual frustration.

Won’t we produce an excess of women? Yes, but the consequences would be very different. There would probably be less, not more violence. Given that most women seem to want to keep men around, a dwindling male contingent might have better sexual chances. Women, for their part, might become more bisexual, doubling their fun. Some, no doubt, would choose to give birth to boys.

Sexual science fiction aside, male-less reproduction could be just around the corner. Some ethicists will object—some indeed decried the process that gave us Louise Brown—but the ethical dilemma here is about choice. Legal same-sex marriage has swept the land, and if not only two lesbians but (with a little help from their women friends) two gay men want to join their biological essence as other couples do, and see in the faces and lives of their children the strange joy of two literally becoming one, whose moral compass would lead us to deny them that choice?