Within 20 to 40 years, sex will no longer be the preferred method of reproduction. Instead, half the population with decent health care will–no shitting you–have eggs grown from human skin and fertilized with sperm, then have the entire genome of about 100 embryo samples sequenced, peruse the highlights, and pick the best model to implant. At least that’s what Stanford law professor and bioethicist Hank Greely predicts in The End of Sex and the Future of Human Reproduction. But skin-grown humans aside, how long until we have “designer babies”?

Here’s where we are: a gene-editing tool called CRISPR/Cas9 has produced a variety of terrifying wonders over the past few years. In August, a group of scientists announced that they had successfully edited a human embryo to eradicate a heart condition. (The validity of their paper, published in the journal Nature, is now disputed, but Chinese scientists also claimed to have edited embryos in 2015, though with less success.) And “designer pets” are already within reach; mice have been turned green. Beagles have been doubled in muscle mass. Pigs have been shrunk to the size of cocker spaniels with “designer fur.” Woolly mammoths are being attempted.

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Greely expects human selection to be less like the Build-a-Bear workshop which “designer pets” suggests, in which you start from scratch with a base animal and pick features from a menu, but rather in which prospective parents select from a pot of about 100 embryos made by two people for preferences like gender and health, and maybe tweak out the hereditary diseases with CRISPR/Cas9.

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Hank Greely

Director, Center for Law and the Biosciences at Stanford University, author of The End of Sex and the Future of Human Reproduction

I think that when average readers hear the term “gene editing,” our minds jump to Gattaca or a build-a-bear workshop for babies where you walk into a lab and select desirable traits (strength, beauty, intelligence, etc) from a pamphlet.

I think GATTACA was much more about selection than about editing, but, yes, most people have an exaggerated view of what is possible.

We don’t know anything, really, about genes that give increased IQ. I suspect–and in my book, The End of Sex, I predict–that in 20 to 40 years we’ll know a little, but not much–maybe enough to say “this embryo has a 60% chance of being in the top 50%” or “a 13% chance of being in the top 10%.” Intelligence is just too complicated and despite decades of work only genes associated with very low intelligence have been found.

Note, though, that you said “genetically select”–selection is more about preimplantation genetic diagnosis [PGD, pre-screening for genetic diseases in embryos] and picking among embryos randomly created by a couple. Editing is intentionally changing DNA away from what the couple created. Neither, though, works worth a damn unless you know what the relationship between the DNA and the trait is and not only aren’t we close with intelligence, we may never be very good at it: too many genes are involved, along with too much environment and too much luck!

…On eye color, hair color, skin color, etc., we’ve got some clues now and will be pretty good in ten to 20 years–though I doubt CRISPRing embryos will be shown to be safe and ready for clinical use in less than 20 to 30 years. On IQ, math ability, sports ability, music ability, personality type we’ll have some information but probably not very much: 60%, 70%, maybe 80% chances of being in the top half but not 90 to 100%. … Right now, though, we have made almost no progress on those traits or on common complicated diseases like asthma, type 2 diabetes, or depression.

… The more simple genetic diseases like Huntington’s disease turn out to be quite rare–common diseases are usually a mix of heavily genetic, somewhat genetic, and not at all genetic. For example, 1% of people with Alzheimer disease (and so about 1 person in a 1000 in the population) have an early onset form that is very strongly genetic. If you have the gene variation involved, the only way you won’t get the disease in your 40s or 50s is to die first from something else. About 4% of the population have two copies of a genetic variation that gives them a 50 to 80% chance of getting AD, compared with the overall average 10% or so. About 20% of the population has one copy of that variant and has about a 20 to 40 percent chance. About 2% of the population has two copies of a different version of the same gene and seem to have zero chance of getting AD. And most people with Alzheimer disease have no copies of any of the known, strong genetic risk factors for it. That’s what most common diseases are like; most behavioral traits will likely be even worse.