Are Genes Our Puppet Masters

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Author: John Timmer

DNA strand with code

The afternoon sessions at the Nobel Week Dialogue covered a lot of ground, which was inevitable if you put six extremely smart people on the stage, give them a topic, and set them loose.

Although there’s no way to summarize the full conversation, it’s possible to pull out some important themes that the speakers returned to. I’ll attempt to do that for the discussion on genetics and the environment.

One of the things that became clear at this panel (and more generally through the day) is that we may have become a bit sloppy in our thinking about heritable and environmental influences on human health and behavior.

If we don’t attempt to form clear hypotheses and demand evidence to support them, there’s a chance that we’ll end up accepting things that appeal to our personal biases.

That may sound a bit dry, but it played out in dramatic fashion across the course of the panel, in part because of the prickly presence of James Watson.

Our genes, our identities?

Geneticist Mary-Claire King started out by strongly arguing against genetic determinism, or the idea that your genes are necessarily your destiny. Throughout the panel, people pointed out that things like a rich early childhood environment had a profound impact that persists throughout a person’s life.

It was also noted that, in some cases, genetic risk factors for diseases like high blood pressure may be significant if a person lives in some cultures, but irrelevant in others, as environmental influences swamp the (relatively minor) predispositions influenced by genes.

If genetic determinism were dead, however, the panel as a whole wasn’t ready to bury it. At the far end of the row of chairs, Jim Watson, co-discoverer of the structure of DNA, was visibly squirming during the opening statements. Watson has a history of inflammatory remarks on this topic, saying that there are genetic differences in intelligence among the races and sexes.

Although he skirted those subjects here, he still managed to stir up the panel by saying that the resistance to genetic determinism was partly social, saying, “the middle class does not like to hear they’re limited by their genes.”

Buried within the bombast, though, was a valid point: there’s strong evidence that schizophrenia has a strong genetic component, and we all seem to accept that. Why is there so much resistance to the idea that positive mental attributes can also be inherited?

This was one of the first of several points where King called for more rigor and the generation of specific hypotheses (about either genetic or environmental influences) that we can test. Without them, we’re likely to accept or reject weaker evidence, in part because it supports positions we favor for ideological reasons.

Somewhere in the middle of this, Helga Nowotny (President of the European Research Council) dropped a term that kept cropping up all day: epigenetics. This term refers to persistent changes to DNA that don’t affect the actual sequence of bases; typically, they involve a chemical modification of bases or changes to the three-dimensional DNA packaging.

Epigenetic changes can persist through multiple cell divisions and, in some rare cases, can be passed on to offspring.

For a number of people, including Nowotny, epigenetics nicely explains how things like early environmental influences can end up looking like stable genetic differences. Again, Watson wasn’t buying it, saying that “epigenetics is used for a lot of crap, and it’s used by people who don’t like genes.”

But again, buried in the rhetoric, he had a point, one that other members of the panel were willing to put in more convincing terms.

We simply don’t have any evidence that epigenetics does much in humans, aside from being involved in a few rare mental disorders. We certainly don’t have any evidence that it can lead to the inheritance of an acquired behavior in humans—the closest we come is a single study in rats.

In fact, King suggested that, when it comes to epigenetics, “we have a semantic problem that’s becoming a philosophical problem, and on the verge of becoming a dangerous political one.” Over the past few decades, the definition of epigenetics has broadened. “Epigenetics” was once strictly used for those rare cases where something was inherited across generations without involving a change in DNA sequences. Now, biologists use it for things that can be inherited when a cell divides, and so persist only for the lifetime of a single individual.

Partly as a result, epigenetics has touched on more and more areas of research. But King seemed to be warning that there’s a danger that people are misreading evidence that epigenetics may be involved in things like health and behavior, and jumping to the conclusion that epigenetics explains everything about them.

If we do that, there will be a temptation to ascribe all sorts of things to epigenetics without evidence. The social consequences of doing so aren’t obvious, but a number of speakers (including, at some points, Nowotny) appeared to be close to doing just that.

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