Genes Or Environment . . . Or Environment?

Forty or fifty years ago, psychologists and other scientists talked about “genes” determining this or that. (James Watson still talks this way.) A certain percentage of the variation of this or that (e.g., intelligence) was attributed to “genes”. Hardly anyone outside genetics or behavior genetics knew what this meant, but many people thought they did. In reaction to the huge misunderstanding (e.g., those who said intelligence was “80% genetic” but did not know what this meant), psychologists began to talk about gene-environment interaction. “Is the area of a rectangle determined by its height or its width?” they like to say.

But notice how fact-free this view is. A tiny number of studies have observed gene-environment interactions but they are very difficult. I think this has made it hard to realize something basic and important. Years ago, I heard a talk about squirrel circadian rhythms by Patricia DeCoursey, the scientist who introduced the concept of phase-response curves. At her talk, she showed results from about 15 squirrels. She tested each one — with an emphasis on individual results that resembles self-experimentation — to determine how much light it needed to become entrained to a 24-hour light/dark cycle. One squirrel needed much stronger light than the others.

Here was an interesting finding that another scientist might have missed. What did it mean? Because the squirrels lived under very similar conditions (e.g., identical diets), it was almost surely a genetic difference. Let’s assume it was. In nature, sunlight is plenty strong. The lab light was weaker. In nature, the genetic difference wouldn’t make an observable difference. Only under artificial conditions did it become visible. It only became visible when the artificial conditions didn’t supply enough of something important (sunlight). In other words, the newly-visible genetic difference implied there was something lacking in the artificial conditions. The genetic difference implied the environment mattered. The opposite of the usual interpretation.

I don’t know any reason to think this is an unusual case. Aaron Blaisdell told me a story that shows its relevance to human health. Aaron is unusually sensitive to sunlight. Until recently, he could only spend 5 or 10 minutes in the sun before it became unpleasant. The condition is genetic. His mother has it; her father had it. It’s called Erythropoietic Protoporphyria. It is autosomal-dominant. Scientists even know where the gene is. That’s where the understanding of most scientists stops. A genetic condition. Recently, however, Aaron drastically changed his diet with great results, as noted earlier. At the same time as the dietary changes, his sun sensitivity got much better. He can now stay in the sun for an hour or more without discomfort. This is a gene-environment interaction, of course, but of a particular sort: The genetic effect showed there was something wrong with the environment, just as it did in DeCoursey’s experiment.

Sure, there’s always genetic variation — it’s just usually hard to see. The wrong environment makes it much easier to see. It reveals a range of genotypes, all of which would be harmless in the right environment. So when you come across a “genetic disorder” such as Erythropoetic Protoporphyria, it is likely to imply an environmental problem. No one had ever told Aaron or his mother or her father that their condition suggested that environmental changes would help them.

6 Responses to “Genes Or Environment . . . Or Environment?”

  1. Aaron Blaisdell Says:

    Seth, that’s a nice tie-in with the squirrel study. I think the same theme is discussed in the 10,000 year explosion. The authors suggest that different modern peoples around the world have different mixtures of genes, with some people lacking alleles adapted toward a particular aspect of the environment, such as the Native Americans lacking alleles for small-pox immunity, or Europeans lacking alleles protecting against malaria. The genetic differences are meaningless in the environment to which the people are adapted, but show up when they are placed in the wrong environment (in the NA case the wrong environment was having small pox and other diseases introduced to their location). I think much of the data from Weston Price’s book shows the same thing by showing how poorly many people around the world did on a Western diet of sugar and refined flour. The sugar and flour was the wrong nutritional environment. I really have thrived after moving toward a WAPF / Paleo / Primal type diet. And many people on the paleo and primal forums (e.g., Stephan’s Whole Health Source blog and Mark’s Daily Apple) have reported much lowered sensitivity to the sun after going primal or WAPF. There was discussion on Stephan’s blog of the importance of the correct ratio of omega 6 to omega 3 fatty acids on inflammation which can directly affect sun sensitivity. Getting off of industrial vegetable oils and replacing them with natural fats (e.g., saturated and omega 3 PUFAs and MUFAs) leads to improved gum health, healthier arteries, improved quality of sleep, and lowered sensitivity to sunlight among other things. It all revolves around systemic inflammation.

  2. bennetta Says:

    “In other words, the newly-visible genetic difference implied there was something lacking in the artificial conditions. The genetic difference implied the environment mattered. The opposite of the usual interpretation.”

    I have argued this exact thing many times, as have two medical doctors who are friends of mine, to explain attention deficit disorder. Even fifty years ago, ADD would not have been a problem for most folks as our lives were more mobile. We did a lot more with our bodies back then. Unfortunately, as we became less active, certain individuals became unable to cope. It’s not that the round peg (ourselves) became square all of a sudden, but that the square hole (the environment) became round, creating a problem.

    One of the most popular methods of coping with ADD, as you might expect, is to change your immediate environment to become more ADD-friendly. Indeed, those who are diagnosed later in life (such as myself) probably already did so subconsciously, but were unable to adapt for some reason later on, causing it to become an issue. Myself, I played seven musical instruments by the time I graduated college, because it was the only thing I found I was good at and enjoyed. This doesn’t translate well to real-life scenarios, however, where we are expected to have 40 hour a week desk jobs, pay bills, etc.

    To anyone with ADD such as myself, this environment relationship is obvious, as it is something we have lived with our entire lives. Clearly we are not stupid, yet for some reason we are still at a disadvantage in modern society. In primitive society, something like ADD may have even been a biological advantage.

    “The genetic effect showed there was something wrong with the environment, just as it did in DeCoursey’s experiment.”

    Exactly.

  3. Robert Simmons Says:

    “No one had ever told Aaron or his mother or her father that their condition suggested that environmental changes would help them.”
    I’m quite certain that this is wrong. Surely many people offered suggestions to them. “Wear sunscreen. Put on a hat. Do sunglasses help?” Etc. That they didn’t phrase it the way you might have is irrelevant, as is that all of the proposed solutions either failed or were only marginally useful.

  4. seth Says:

    Robert, by “help” I meant “reduce their sun sensitivity”. I agree, I should have been more explicit.

  5. Varangy Says:

    This post’s title is a strawman: “Genes Or Environment . . . Or Environment?”

    No need to be mutually exclusive, allow me to summarize this post in two words:

    Gene expression.

  6. Why is it hard to stick to a diet? Says:

    [...] Making decisions is hard because we aren’t rational creatures even when we think we are. When it comes to the "listen to you body" advice, you can also change what your body says. Seth Roberts for example recommand to eliminate smell while eating by wearing a nose clip. A nice post from Seth about the nature of what genes determine: Seth’s blog » Blog Archive » Genes Or Environment . . . Or Environment? __________________ I am always open for feedback on my posts. That might focused on the argument at hand or on my writing style. If your feedback would go offtopic feel free to send me a Personal Message. My posts generally don’t contain medical or legal advice, if you have a problem seek the opinion of an expert I don’t believe in Beliefs. Nassim Nicholas Taleb [...]