on EconTalk.Wrong Causation:
About two decades ago people started asking not what was added to the environment, which is a sort of logical way to pursue this question (of diseases), going by history, but what had been removed from the environment that might have prevented the emergence of these diseases.
What is Microbiome?
The microbiome is the collection of microbes that actually lives inside of us. So, microbes in our body right now actually outnumber our cells by a factor of 10 to 1. Ten times as many microbes as you carry cells, your cells. That's because they are a lot smaller than your cells; that's why they all fit. Most of them fit in your gut, but they are really all over the surface of your body. And what's there has a very important implication for how your immune system works. It sort of calibrates your immune system. And there is lots of suspicion that it has sort of changed over the course of the 20th century in particular for many reasons. One is you just simply don't inherit the same microbes because you are not exposed to them, and that's due to improved sanitation and to, interestingly, smaller families--just less crowded. So that was sort of what David Strachan was seeing all those years ago, that there was this correlation with large family size protecting against the younger kids. So that's one direction that all this research is now pointing in. So the hygiene hypothesis essentially starts as this thinking about infections. At this point no one really--well, very few people I should say--really think that infections of the type David Strachan was talking about, which were called measles and that kind of thing, really protect. And that's simply because they can't get a signal of protection when they do these epidemiological studies.
What has been consistent is that kids who grow up with other kids, very young, are protected; they think it's more of a microbiome effect. Kids who grow up with animals--dogs in particular seem to be protective. Kids who grow up on farms seem to be protected. Kids who grew up in situations where they have, as I mentioned, not very good sanitary amenities seem to be protected. And so these things are probably all markers for a transmission of microbes. You have to think of it as an ecosystem. And an ecosystem in science, a more diverse ecosystem is stronger, more robust than a less diverse ecosystem. And for probably some of the same reasons it seems that the diversity of our internal microbiome, our internal system of microbes, is better for our health. The more diverse it is, the better. Now there are of course people coming up with data--you come up with a rule and then immediately someone comes up with data that suggests it's not true. So that's already emerging. But I think for now that's holding as a rule.
Moises is currently reading Taleb's Antifragile:
He talks a lot about hormesis, which is this idea that certain stresses in the right amount--and I would also add at the right time in development--actually make you stronger rather than making you weak. He talks about it in the context of exposure to risk. If I understand it correctly. Small collapses--you are exposing yourself to small vulnerabilities and small fluctuations so that you are much more ready for the large fluctuation that's coming anyways.
We accept this idea in the field of physical health, no problem, which is that daily, semi-daily exercise is necessary just to sort of be healthy. You need to go for a job 30 minutes, 3 times a week, say, because that stress actually improves how your circulatory system works; it strengthens your bones; it strengthens your muscles; it leads to neurogenesis--your neurons are actually generated while you exercise. It's beneficial. And it helps you maintain homeostasis. It helps you keep your balance, equilibrium in daily life. Now, the same is apparently true of the immune system. The problem is the immune system has basically been hidden from view, so we haven't realized it. But apparently the same thing is true, which is that our immune system needs certain influx, certain stimuli that are evolutionarily determined. Because they've just simply always been there. We sort of expect them. And that we need them especially early in life. And again, the parallel example of the importance of early life is brain development.
What has been consistent is that kids who grow up with other kids, very young, are protected; they think it's more of a microbiome effect. Kids who grow up with animals--dogs in particular seem to be protective. Kids who grow up on farms seem to be protected. Kids who grew up in situations where they have, as I mentioned, not very good sanitary amenities seem to be protected. And so these things are probably all markers for a transmission of microbes. You have to think of it as an ecosystem. And an ecosystem in science, a more diverse ecosystem is stronger, more robust than a less diverse ecosystem. And for probably some of the same reasons it seems that the diversity of our internal microbiome, our internal system of microbes, is better for our health. The more diverse it is, the better. Now there are of course people coming up with data--you come up with a rule and then immediately someone comes up with data that suggests it's not true. So that's already emerging. But I think for now that's holding as a rule.
Moises is currently reading Taleb's Antifragile:
He talks a lot about hormesis, which is this idea that certain stresses in the right amount--and I would also add at the right time in development--actually make you stronger rather than making you weak. He talks about it in the context of exposure to risk. If I understand it correctly. Small collapses--you are exposing yourself to small vulnerabilities and small fluctuations so that you are much more ready for the large fluctuation that's coming anyways.
We accept this idea in the field of physical health, no problem, which is that daily, semi-daily exercise is necessary just to sort of be healthy. You need to go for a job 30 minutes, 3 times a week, say, because that stress actually improves how your circulatory system works; it strengthens your bones; it strengthens your muscles; it leads to neurogenesis--your neurons are actually generated while you exercise. It's beneficial. And it helps you maintain homeostasis. It helps you keep your balance, equilibrium in daily life. Now, the same is apparently true of the immune system. The problem is the immune system has basically been hidden from view, so we haven't realized it. But apparently the same thing is true, which is that our immune system needs certain influx, certain stimuli that are evolutionarily determined. Because they've just simply always been there. We sort of expect them. And that we need them especially early in life. And again, the parallel example of the importance of early life is brain development.
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