The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We are Today, by Rob Dunn

The Wild Life of Our Bodies. Predators, Parasites, and Partners That Shape Who We are Today

The Wild Life of Our Bodies is about how we evolved in response to various organisms, from internal parasites to predators, how our bodies are marked by those earlier battles whether they continue today or not, and how that can be detrimental to our well-being.

For example, Crohn’s disease and various other auto-immune diseases are far more prevalent in rich countries than in poor countries, a difference that cannot be fully explained by the fact that people live longer in rich countries and therefore have more opportunity to eventually develop all kinds of diseases. The author wonders if this could be because our immune system is used to fighting certain bacteria and other invaders, and so perhaps the absence of these enemies—due to the fact that we sterilize and anti-septicize everything as much as possible—results in the immune system turning on the body itself.

It’s not like the immune system is an intelligent, conscious being that can respond rationally to changing circumstances after all. It’s kind of dumb and unsophisticated in its way, just doing what it evolved to do, regardless of whether that has beneficial or harmful consequences in present circumstances.

One related theory is that certain parasites emit chemical signals telling the immune system that the volume of parasites in the system is low enough that countermeasures are not necessary. But the immune system evolved to take that into account, in effect to assume the information it was getting about what was in the body was deceptive, that the actual amount of parasites was likely much higher than it seemed. So now when in fact there are few or no parasites presents, it still reacts like the body is under significant attack. This kind of overkill can occasionally have side effects like these auto-immune diseases.

Maybe the immune system needs its old adversaries back, to keep it busy in a productive way, to keep things in balance.

If true, then this would mean our strategy of doing anything and everything to lessen the amount of exposure we have to germs, viruses, etc. is misguided. Surely we don’t want to go to the opposite extreme, but maybe the ideal level of internal threats for our bodies is some amount that’s low but still well above where it is now.

This is all very speculative, but to the Dunn’s credit he never claims otherwise. He presents a theory that is plausible, and points out how it is supported by anecdotal evidence, and by research that is suggestive but not conclusive.

It’s not proven, it’s not consensus science, but there’s nothing about what he’s saying that would render it pseudo-science or something woo woo. At worst it may turn out that further study shows it to be a promising idea that didn’t pan out.

Obviously the anecdotal evidence has only minimal scientific weight. There’s plenty of it in the book, but I suspect that’s more for the entertainment value than because it adds much to the argument.

Some people suffering from Crohn’s and other such diseases have taken to traveling to third world countries to purposely introduce intestinal worms or other parasites into their bodies, to try to restore some balance. What’s creepy is that sometimes they walk around in unsanitary areas of excrement and filth, hoping the right parasite will enter their body. You’d think there would safer, easier, and more efficient ways to do that—and sometimes there is (people were given Gatorade with worm eggs in it in one experiment)—but when a treatment isn’t approved and there are no current experiments you can get in on, I guess you do what you have to do.

This kind of idea is not completely new to me. I’ve long wondered about people who are super strict about avoiding germs, and shy away from letting any junk food in their body, and at the first indication of even a minor problem zap it immediately with medication. Are they just making their body a wuss that has no experience dealing with adversity? Again my evidence would only be anecdotal, but it seems like such people are at least as sickly as anyone else. I don’t know that the ideal for safeguarding our health is to live like bubble boys.

The book isn’t limited to a discussion of internal threats. The author also discusses how we evolved in response to having to deal with predators, and how this too isn’t always best suited to the modern world.

For example—as is painfully and depressingly obvious—rational reflection does not come natural to most humans. That, according to the author, is because our distant ancestors lived in circumstances where acting quickly was more important than acting wisely. If they encountered a lion or sabre-toothed tiger or whatever, the people that instinctively fought or fled were more likely to survive and pass on their genes than those who sought to weigh all the available evidence and think through the very best course of action.

So jumping to a conclusion based on instinct and emotion with little or no thought was a pretty good strategy back then. Now it’s hugely disadvantageous (except to demagogues and Fox “News” folks and such, who make a living by exploiting it).

Dunn proposes that we “rewild” our bodies and our environment. We shouldn’t be so meticulous about making our lives as antiseptic as possible, but should let our immune system do its job by allowing it to encounter some small number of adversaries. Meanwhile, we should introduce, or re-introduce, a myriad of beneficial plant and animal species into our cities, as opposed to the way now the bulk of the species who live with us in cities are vermin that survive in spite of our best efforts at eradication—rats, roaches, bedbugs, etc.

The Wild Life of Our Bodies is well-written, a pretty easy read, at least moderately interesting throughout, and makes a highly plausible case. But not everything that seems plausible to a layman turns out to be true. So I think there’s a good chance he’s on the right track, but I wouldn’t say I’m fully convinced.


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