why you can’t design your baby and why it’s a terrible idea to try

Despite dire warnings, we may never be able to custom design humans. And if we ever learn how, we may accidentally drive ourselves into extinction if we try.

happy baby

Modifying human genes sounds like the stuff of science fiction, but we are actually living in a world where the day when doctors tinkering with the very biological building blocks that make you who you are is right around the corner. We’re already testing genetic engineering to defeat very aggressive and hard to treat cancers, or at least arrest tumor growth, on live human patients. So it wasn’t actually much of a stretch when an American team of researchers modified single celled embryos using a state of the art gene editing technique known as CRISPR.

None of the embryos were meant for implantation, but this success means that embryos likely to have easily identified and well understood genetic defects that could result in disease or disability later in life, can be altered before they develop and are carried to term. Some genetic diseases might even be wiped out this way given enough children and generations. From a purely utilitarian standpoint, this is really a triumph in the making if used in tandem with modified viruses capable of altering existing patients’ DNA in the course of several weeks.

Of course, a lot of work still remains to be done, especially studies into long term safety and efficacy before this is something available at your primary care doctor’s office. But the rapid progress is already raising heckles that a generation of designer babies could be on the way, and a Chinese scientist even tried to illegally modify two babies using the technique, although he did it poorly and his tinkering probably had little to no effect. At the same time, you can just imagine parents sitting down with a genetic planner, GATTACA style, and customizing how exactly their baby will look like and what talents it will have as an adult 20 years from now.

It’s like a eugenicist’s dream, not to mention the way many sci-fi horror movies start, with scientists modifying our genes and discovering terrifying consequences. However, this is a gross oversimplification of both the challenge in genetic engineering and the sheer scope and complexity of the biology involved. A human has about 19,000 genes. Some code for a protein, others regulate a particular function, others are old, inactive junk, and others came from benign viral infections of our ancestors and may or may not play a role in how we develop, grow, and age. On top of that, our exposure to pollution, hormones, and the conditions during our development all play a role how those genes tend to express themselves from conception to death.

why modifying genes is such a tricky business

Don’t get too hung up on the number from a big picture standpoint, though. We’re not the most genetically complex or diverse living things in existence by any stretch. The humble grape has over 30,000 genes by comparison. An extremely rare Japanese flower has some 150 billion base pairs of DNA while we have a measly 3 billion. Yet those 3 billion base pairs contain a whole lot of ground for genetic engineers to study and potentially tweak, and many of those modifications might cascade down to millions of other base pairs.

Now, you may remember the Punnett square from middle school biology in which you plotted how likely an organism was to inherit a feature. That’s a good way to introduce the basics of genetics, but unless you know for a fact that a single gene controls that feature, completely useless for predicting if changing that gene will make any appreciable difference. For example, eye color is controlled by something like 16 different genes and 679 are involved in regulating height throughout a person’s life, while mutations in two genes determine your risk for breast cancer.

That said, there are single gene genetic disorders like Huntington’s, cystic fibrosis, and muscular dystrophy. Being able to shut them off or edit them out at the right stage of development or growth, if not just at any point in life, would cure them. CRISPR should be fantastic at doing exactly that and making other well-defined and targeted changes in embryos. If you are a carrier of such a single gene disorder and so is your partner, a safer route for your future child would involve editing an embryo through IVF instead of just hoping that he or she will just be a carrier too.

But as you saw, eye color and hair color are controlled by a lot more than a few genes and those genes can be altered by everything from hormones in the womb to environmental pollutants. Our genome didn’t evolve for easy, modular editing in the future. It evolved in response to diet and stressors in our ancient past. If you wanted to make sure that your child was 6′ 3″ tall, weighed no more than 200 pounds, and was really good at football, that’s going to involve total 24/7 control over thousands of genes and the child’s environment from the moment of conception.

the dark, evil elephant in the room

Maybe this could be possible one day, but it certainly won’t be any day in the foreseeable future, and it definitely wouldn’t be practical if it was ever possible, or even remotely advisable. The kind of eugenic thought which gripped the world in the early 20th century and kicked off the Holocaust was actually based on a profound misunderstanding of statistics, and very pseudoscientific approach to evolution. Basically, Francis Galton and his followers mistook more people becoming literate and educated as a rise in mediocrity through a mathematic concept known as regression toward the mean, triggering a wave of racist and classist alarmism.

Eugenicists were worried that their “superior” genes were being corrupted by interbreeding between classes and races, that genetic diversity was just dragging them down towards brutish mediocrity. It’s a train of thought you can still find resonating among today’s racists, or ethno-nationalists as they like to call themselves. But this worry reveals a profound lack of scientific understanding that’s fairly critical to any future effort to modify DNA, and shows they’re using the wrong ways to measure human progress.

Genetic diversity is essential for any species to survive and adapt to its new environment. Without a significant enough library of genes that can help us deal with a future stressor, we may be unable to cope with drastic changes in diet or new diseases that come at us. Similarity in genes results in severe inbreeding, making us a lot more vulnerable to an environmental blow that could kill off an entire population without giving it a chance to develop any useful mutations. History is replete with examples of inbred organisms dying off when climates changed or during disease outbreaks.

Ultimately, this is why even in a far future where we can customize children, we have to be extremely mindful of allowing diversity and not messing with too many genes which could one day contribute to disease resistance, or give us the ability to adapt to a new diet. Nature doesn’t necessarily care if we’re getting high IQ scores because those are fairly arbitrary, and are much closer correlated to household values and income than biology. It’s also completely disinterested in our athletic prowess or how conventionally attractive we are to a particular culture. It only cares about reproduction rates.

how we could engineer ourselves into an endangered species

In fact, in the grandest scheme of them all, nature is a series of trials which test random organisms with random genetic make-up in different climates with different resources and against different stressors. The ones able to live long enough to reproduce and pass down their genes are successful, even if they don’t end up with long lives and building civilizations that explore new worlds. Evolutionarily speaking, we’re pretty successful, but nowhere near as successful as insects or bacteria which typically live fast, die young, and are constantly reproducing in large numbers. Our notions about the evolution of intelligence being some sort of necessity to survive is little more than a narcissistic delusion.

If we take the reins of our genetic diversity and development, we could end up steering ourselves into very specific arbitrary niches which prevent much of the necessary genetic randomness that allowed us to adapt to changes in our environment for the last 150,000 years. We would end up being really well suited for completely artificial stressors and with little ability to cope with really profound changes in our food chain, kind of like the Hiteks in the dystopian speculative anthology Man After Man by Dougal Dixon. Our end could be swift, brutal, and triggered by something we’d find trivial today because collectively, we have the necessary defenses against it.

But this doesn’t mean we should treat genetic engineering the same way we treat our nuclear weapons and let nature play out as it will. There are plenty of arguments for a middle ground approach in which we tackle obviously harmful mutations and edit devastating errors out of existence, but back off trying to customize future humans because we’d most likely fail miserably in the task due to the complexity of our biology, or steer that population to an extremely precarious existence only possible in an artificial environment.

As Uncle Ben told Spiderman, with great power comes great responsibility, and there are few fields of science where this applies more than the future of genetic editing in humans. We have the potential to do immense good for billions of people. But there’s also the possibility that if we’re not mindful of the long term effects of our actions, we could help a new Black Death cull a continent, or even worse, our days could be numbered in a way that’s not too dissimilar from countless dystopian sci-fi movies and novels.

[ this article originally appeared in Rantt Politech and has been updated ]

# science // designer babies / genetic engineering / genetics


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