Archive for January, 2017


No, gene editing won’t ruin human evolution

Friday, 13 January, 2017

An article published in TIME magazine by Jim Kozubek, titled “How Gene Editing Could Ruin Human Evolution” basically argues that it’s too risky to edit our genes. I’d agree with most of these risks, but none of these risks are insurmountable and none of them are good arguments for preventing gene editing entirely.

Genes are complicated, but not impossibly complicated

It is definitely true that most traits are controlled by many genes, and that many genes control many traits. As Kozubek says:

Biology is robust against breakdown. It straddles risk like a money manager, and that straddling of risk over the entire genome is one reason there are so few single “targets” for many of these psychological and cognitive traits. Indeed, many of these genetic variants may be pleiotropic, meaning they have different, often unrelated effects in different cells or tissues

This does certainly complicate any potential gene editing, as many areas of the genome would need to be edited and these might have unintended consequences. But this added complexity is still solvable. If gene editing technology is good enough, there’s no reason we can’t edit half a dozen areas of the genome instead of just one.

Furthermore, if one gene does have different effects in different tissues, that just increases the complexity of the genetic engineering problem but still doesn’t make it impossible. With somatic genetic engineering, one could target the genetic edit to just one organ (like the brain), without it effecting that gene in the rest of the body. One could also potentially duplicate the gene entirely and edit only one copy, plus adjust the regulatory sequences so that the edited gene is the only one expressed in the tissue of interest and the unedited gene is the one expressed in other tissues.

Gene editing isn’t about what is right, but what is right for each individual

Kozubek seems to to come very close to saying that scientists don’t understand evolution and that genetic diseases don’t exist, when he says:

Second, scientists tend to think of men as machines, genes as their broken parts and variations in life as problems to be solved—aberrations outside the normal curve. This assumes there is a right way for genes to be. In reality, Darwin showed us that evolution does not progress toward an ideal model or a more perfect form, but instead is a work of tinkering toward adaptation in local niches. Nowhere in nature does it say how a gene should function.

Genes have a fitness, which refers to how successfully those genes allow the organism to reproduce in a particular environment. But we, as humans, also can place value judgement on certain phenotypes (traits an organism possess) that may or may not correlate with fitness. For instance, a genetic disease that causes an increased chance of an early death decreases fitness and is something most humans don’t want. But sometimes a gene might increase your fitness, perhaps by making you super fertile, but you as a human still don’t like that trait. And some traits we might want, like to be able to eat as much we want without getting fat, may decrease our fitness in some environments where food is scarce or increase when food is plentiful. Basically, there’s not really a correlation between what evolution is aiming for and what we humans are aiming for.

The argument that scientists are trying to restore genes to their natural, correct or ‘healthy’ state is a fundamental misunderstanding of what most proponents of genetic engineering want. We want to be able to give people the freedom to choose what genes they, or their children, have. Indeed, this is one fundamental issue with the notion that we should only use genetic engineering to make people healthy but not do anything like enhancement: there isn’t universal agreement on what healthy is. What many of us might think as natural or ‘healthy, such as being able to hear, might be considered by some as an unwanted disability.

Diversity does not trump autonomy

Similar to the first argument, Kozubek argues that certain things thought of as diseases or disabilities can offer advantages in fitness in certain contexts.

Furthermore, genetic variants that predispose us to risk or supposed weaknesses are precisely the same ones that turn out to have small fitness advantages (they make us better at numbers, more sensitive, alter concentration…). This is one reason I am a “neurodiversity advocate.” Evolution works at the margins, and it does so through trade-offs: Often, you don’t get an advantage without risking a disadvantage. This is not trivial.

It is undoubtedly true that all advantages come with disadvantages, just as all drugs come with side-effects. As I alluded to above, a gene that increases risk of obesity in modern society might offer a significant advantage in a food-scarce environment. A genetic enhancement that allows humans to see in ultraviolet light might require allowing so much UV light into the eye that it increases the risk of macular degeneration. An enhancement that increases wound healing by preventing scar formation might increase the risk of infection.

One key point to this, however, is that these are all environmentally dependent. Our environment now is very different to what it was when we did most of our evolving, as we now have a lot more food, the ability to produce sunglasses to block UV light and enough antiseptics and antibiotics to prevent infections when they occur. I simply don’t see how somebody could argue that the mutation in the CFTR gene, which causes cystic fibrosis if you have two copies but resistance to tuberculosis if you have one copy, is a worthwhile trade-off in Western nations where tuberculosis is very rare.

The other key point point is that people should be informed of the risks and benefits and allowed to make their own choices for gene editing (within a broad ethical framework, of course), just as we do with pharmaceutical treatments. For example, some might see an increased risk of autism as a fair cost for greater mathematical ability, whereas others may not. Even if having a diverse set of genes in the population benefits the species somehow, I certainly don’t think we can use this to justify forcing people to keep, or pass on to their children, the genes they have. Are you really going to cite the need for genetic diversity in human evolution as a reason to deny a patient a gene therapy they desperately desire? Are you going to make somebody deaf in the hope they become a genius composer like Beethoven?

Evolution will continue

The final point, relating to the  later points, is that genetic engineering will break evolution:

And genetic risk variants remain in the population because they’re advantageous to certain people, given the right genetic background or conditions. Those risk variants are speculating—evolution, always and forever, takes chances.

The problem with this is that it assumes that gene editing will somehow decrease the genetic diversity in the population.  As I briefly mentioned a while back in response to an SMBC comic, there is no reason to think this would be true. Yes, we’re likely to get rid of many of the genetic diseases that we can, because most people see those as bad things. But there are many traits where there is little consensus over which is better, and may companies may have different techniques to produce these traits, so diversity of these genes may increase.

We’re also likely to transfer genes from across the natural world (like fluorescent proteins from jellyfish) or create entirely new genes. This process of adding and editing our genome is vastly faster than waiting for mutations, so there will be ample variation in the population.

Human evolution will definitely be different, but it will still continue. But that’s no different to any other treatment or technological intervention that changes how often we pass on our genes. Whenever humans treat the sick or help our injured, we’re altering the progress of evolution. But this doesn’t make medicine or technology bad. In fact, these things are probably pretty good, even if they change evolution. And so, even if it changes our human evolution, I think gene editing will be pretty good too.