Gene editing can make us different, but not better
For such flawed creatures, human beings are surprisingly hard to improve, at least through our genes.
That’s one reason there’s so much outcry over the recent claim that researchers in China altered the genes of a pair of twins girls — endowing at least one with resistance to HIV. The genetic change, even if it worked as advertised, would not be a clear-cut improvement but a trade-off.
The claim is that the researchers disabled a gene called CCR5, which in its intact form helps HIV enter cells. Getting the disabled version, which occurs naturally in some people of European ancestry, would most likely make the girl more susceptible to influenza and a class of infections called flaviviruses, including West Nile. Preliminary reports suggest the researchers succeeded in changing only one of the two copies of the gene in the other twin, which is not enough for HIV resistance (or flavivirus vulnerability).
Did the twin with the alteration receive a better version of the gene than she would have otherwise been born with? No, said Hank Greely, director of the Centre for Law and the Biosciences at Stanford University. “CCR5 is found in just about all mammals,” he wrote to me in an email. “It’s probably doing something useful.” We don’t know all the risks of disabling it, but in his view, the benefits are “small to nonexistent.”
Indeed, simpler, safer methods of preventing HIV have advanced so much that doctors are starting to consider the possibility of a total eradication campaign. The benefit of the girl’s modified gene would vanish along with HIV, but its downsides would remain.
And yet, people can’t seem to get over the perception that genetic engineering will not only improve but perfect humanity. A 2015 headline in MIT Technology Review read “Engineering the Perfect Baby,” below which was a story about the technique, Crispr, that purportedly was used by the Chinese scientists to modify the twins.
Maybe the perfection misconception stems from the ease with which scientists can improve plants and animals through genetic engineering. But there, improvements aren’t made for the sake of the plants or animals, but for the people who make money from raising or selling them. So we have faster growing salmon, goats that produce valuable (to us) proteins in their milk, and corn that resists heavy spraying with herbicides.
How could this kind of “improvement” apply to humans unless someone is thinking of us as a commodity? Only in dystopian stories does anyone use genetic modification to make people hardier soldiers, more efficient factory workers, or in some other way better able to serve corporations or the state.
There are some legitimately bad genes, and scientists are working on so-called gene therapy to help people who’ve inherited them. But there are already safe ways for genetic diseases to be avoided, rather than edited. If people want to have children biologically and know they carry a mutation that puts their offspring at risk for cystic fibrosis, haemophilia or another serious genetic disease, they can opt for something called pre-implantation diagnosis. This is essentially genetic testing of embryos produced through in-vitro fertilisation to ensure only ones without the deleterious mutation are implanted.
There are rare cases where genes can be both common and seemingly undesirable. One of these is a gene called ApoE4. There are two other versions of the gene floating around in the human gene pool – ApoE2 and ApoE3 – and people inherit one copy from each parent. Getting one copy of ApoE4 puts you at three to 10 times the average risk of getting Alzheimer’s disease. Getting two copies of ApoE4 puts you at even higher risk.
I used ApoE4 as an example of a potential gene editing target when I wrote a previous column on the topic back in 2015. Soon afterward, something astonishing was discovered. Scientists studying a South American hunter-gatherer group called the Tsimane found that people with ApoE4 had a lower risk of Alzheimer’s – the opposite of the effect on typical subjects – but only if they also had certain parasites. Because most Tsimane people had parasites, ApoE4 was beneficial.
Parasites affect the immune system, and some growing evidence indicates that Alzheimer’s disease is triggered by an inappropriate immune system response to proteins in the brain. This opens up the possibility that in the future — by the time today’s babies are middle aged — scientists will have figured out how to simulate the effect of parasites, and people with one or two copies of ApoE4 will be at less risk than the rest of us.
Life on Earth has been evolving for around 3.8 billion years – and yet our planet has yet to produce any perfect species. Even cats have their flaws. As palaeontologist Neil Shubin explained in his book “Your Inner Fish,” evolution has a limited palette and tool box. We’re stuck with a genome and basic body plan that’s been gradually modified from the time our ancestors were fish. Design flaws that cropped up in repurposing that fish body have led to everything from hernias to hiccoughs. There is likely no road to perfection from here.
That won’t stop people from trying to improve our genes. It seems inevitable that someone will eventually try to sell people genetic tweaks to give their kids a higher IQ. Who knows? Such a thing might make some of us quicker, but probably not wiser.
The views expressed are personal