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“Why should only the tall have access to tall genes? And why should only the smart have access to smart genes?… our goal is to give as many people as possible the opportunity to choose their genes for themselves (and their descendants) rather than simply accept inherited genetic inequality. Because genetics shouldn’t be a lottery.”

That’s the pitch of , a start-up openly aiming to one day offer would-be parents the chance to genetically enhance their children. I’d say the children of anyone who could afford such a service will have already won life’s lottery, but the more immediate question is: could we really genetically enhance our children if we wanted to?

To get a sense of what might be possible, I started with maintained by biologist George Church at Harvard University. When I asked Church what the list is for, he told me he started it as an answer to questions that came up while giving lectures, ranging from whether all rare gene variants are harmful, to what kinds of genetic enhancements might be possible. The list is popular with transhumanists who want to use genetic engineering to create superhumans.

So, let’s take a look at what’s on it.

Would you really want extra fingers?

The list is rather a mixed bag. It now contains over 100 items, but only around half are specific gene mutations or variants that have been identified in people and linked to specific effects (the rest relate to animal studies or medical trials). Church has picked out mutations that might have an unusually large “positive effect”, from protecting against certain diseases to reducing male aggression.

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To me, some of the traits on the list are anything but desirable. For instance, it states that unspecified changes in one gene could improve a person’s “manipulation ability” by giving them six fingers on each hand. Would it really? Would you want six fingers even if it did? Imagine trying to buy gloves!

Also listed are two gene deletions that result in insensitivity to pain. But this isn’t an enhancement: children who can’t feel pain are known to end up with horrible injuries.

Most of the rest of the traits on the list fall into the “nice to have, but not worth resorting to genetic engineering for” category for me. Take “low odor production” – it hardly seems essential in the age of deodorants. Sure, I’d like to be able to hold my breath for longer or cope better at high altitude, but I’m not sure any of my descendants would care.

Only a few variants on the list have been linked to broadly appealing traits such as living longer or having higher intelligence – that is, to the kind of thing that rich would-be parents might pay for. But we’re still very far from the point where we could be sure that engineering these variants into children really would make them smarter or live longer. We simply don’t know enough.

Engineered to sleep less – but at what cost?

For starters, it may turn out that some of these associations are wrong, that some of the gene variants don’t have the effects we think. Or they could have the desired effect only in conjunction with certain other genetic variants.

What’s more, there are often trade-offs. One variant associated with higher intelligence, for instance, may increase the risk of going blind later in life, according to Church’s list, while resistance to norovirus might increase the risk of Crohn’s disease. I think I’d rather be a little stupider and endure the occasional bout of norovirus. You might feel differently – and your future children could end up thanking or cursing any choices like these you make on their behalf.

No downsides are noted for most variants on the list, but that doesn’t mean there aren’t any. Take the variants associated with sleeping less, for instance. Given the vital importance of sleep to brain health, it seems very likely to me that there are some trade-offs.

What I don’t think many people realise is that not only is our understanding of genetic variants like these very much in its infancy, in many cases we may never be able to be sure whether a specific change will be beneficial. That’s because to determine the good and bad effects of a genetic variant, biologists need to look at tens of thousands of people who have it, or even more.

How we can really make life’s lottery fairer

This means that to maximise the odds that any one individual really would benefit from genetic engineering, you’d have to make dozens or hundreds of changes at once. This is especially true for the traits mentioned by Bootstrap Bio, because height and intelligence are determined by hundreds of variants that each have a tiny effect. The catch here is that we don’t yet have the ability to safely make a few changes to human embryos, let alone hundreds at a time, as I discussed in my previous column on preventing inherited diseases.

I’m not saying all this because I’m opposed to genetically enhancing our kids. On the contrary, I’m actually in favour – it’s better than letting children’s fates be determined by random rolls of the genetic dice. But I’m very far from convinced that we should attempt heritable genome editing anytime soon. And to get to the point where we could seriously consider it, we don’t need start-ups like Bootstrap Bio. What we need instead is to massively expand studies like the UK Biobank, which is following large numbers of people over several decades, to get a much clearer ideas of the pros and cons of genetic variants like those on Church’s list.

As for the idea that companies selling genetic enhancements will make the world fairer, pull the other one. A born around the world today end up shorter than they should be and with impaired cognitive abilities because they don’t get fed properly. Even more don’t get a good education. Anyone seriously concerned about taking the lottery out of an infant’s chances in life might want to focus on ensuring these millions of children can reach their existing genetic potential, rather than trying to boost the genes of a few.

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