The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We Are Today by Rob Dunn
My rating: 4 of 5 stars
Dunn’s book addresses a host of intriguing questions such as:
-Why are there diseases that disproportionately attack those in the richest parts of the world while being almost non-existent in poor countries?
-Why is obesity at epidemic proportions among modern humans?
-Why—while people have diverse tastes overall—do there seem to be universal preferences for sweet, salty, and fatty foods?
-Why are so many people’s lives wrecked by constant stress and worry?
-Is the Appendix really a vestigial organ with no apparent purpose?
As the subtitle suggests, this book is about the role that other species have played in human evolution and the way we look, behave, and think today. The message of The Wild Life of Our Bodies is that humanity’s proclivity to see itself as an island–uninfluenced by other species–has its cost.
The book is popular science–approachable to a layman but with the usual disdain for gratuitous assertions and shoddy reasoning that define the scientific though process. That being said, Dunn does put some editorial opinion out there in ways that might appear as fact in a slipshod reading. The most prominent example being Dunn’s suggesting that what best defines humanity is not our intelligence or ability for abstract representation (or even our physical appearance), but that we are the only (first?) species that has killed other species off not purely of self-defense or for food, but to exercise control over our ecosystem. I doubt this would strike a majority of impartial scientists as a fair and unbiased way to define humanity. Granted, this point not what The Wild Life of Our Bodies is about, and whether one thinks this it is fair or not is not critical to whether one will find the book to be of value. However, the idea (and the fact) that humans have zealously killed off other creatures is certainly relevant to the discussion at hand.
If “terraforming” is the term for how an alien race might environmentally engineer Earth to make it suitable for them to live here, perhaps we could call humanity’s assault on other species “bio-forming” of the planet—choosing a roster of species that strikes our fancy. All the time humans were trying to make ourselves more comfortable by getting rid of inconvenient species, we remained ignorant to the downside.
Dunn covers a broad range of mismatches between who we are evolutionarily and how we live in the modern world. The Wild Life of Our Bodies suggests that, like the pronghorn antelope, humans are in many cases over-designed because of the loss of species (parasites, predators, symbiotes, etc.) that helped to make us who we are today. (One question that once puzzled biologists was why pronghorns were so much faster than every species they faced.)
While it sounds good to be over-designed (at least relative to the alternative), it’s not without cost. In our case, we had guts that were supremely adapted to having parasites, but the lightning fast (on an evolutionary timescale) elimination of those parasites has left us with bodies that attack a non-existent enemy and this has resulted in a number of new diseases. We are used to diseases that succeed in the poorest—and, hence, least hygienic areas– but disease that mostly attacked in the cleanest places on Earth have puzzled us for some time. Crohn’s disease is a prime example. “Rewilding” (i.e. putting parasites back into) the guts of Crohn’s patients has shown positive results.
Dunn lays out a couple of the theories as to how the loss of our intestinal bacteria may result in a number of first-world ailments. Interestingly, some of these diseases aren’t even digestive in nature, and might seem to have no logical connection to gut bacteria. However, our body’s systems are a system-of-systems—i.e. they are integrally linked. One issue is that some parasites have been able to mask their presence, and our bodies have learned to present a heightened response to account for this veiled threat. Today our systems can’t tell the difference between our squeaky clean guts and a gut full of these sneaking parasites so it drops the immune system version of an A-bomb.
This is one example of why some diseases don’t exist in the third-world where the body knows what parasites it’s up against. One might say, “Yes, but these ailments of over-reactive systems can’t be as bad as the effects of the parasites.” That’s often not true. Most people with internal bugs (we all have them to some degree), don’t even realize it. The fact that people with Crohns’ are willing to have predators implanted in them speaks to this issue.
There has been concern for years about downside of the rampant use of anti-bacterials, antibiotics, and antiseptics, and this is a topic Dunn addresses as well. For example, there seems to be little evidence that such agents in soap do any particular good, but they decidedly do bad (encouraging drug resistant species.)
Perhaps the single greatest change in the nature of homo sapiens life resulted from the agricultural revolution, and Dunn delves into how this seminal event changed our bodies. With paleo-dieting all the rage, it will come as no surprise that there have been some major changes to the human diet since our hunter-gatherer ancestors roamed the Earth. Once again, we have bodies built on an evolutionary timescale, and they don’t necessarily cope well with our new diets.
One problem is that we have strong hardwired drives for foods that were a rarity in our species’ past, but which we now produce in abundance. For example, we eat far too much refined sugar because our bodies are wired to love sweet, but that kind of food was rare to our pre-agricultural ancestors. Hence we have the existence of diabetes, and its greater prevalence where high-sugar diets are common. Many people are also saddled with an evolutionary advantage to store fat because their ancestors come from a clime where food was not abundant year round. The problem is that now there’s a grocery store on every corner and this once great advantage is contributing to burgeoning waistlines.
I gave this book a high rating on the grounds that it presented a lot of food for thought, and that’s what I most value in non-fiction. Some of the theories may turn out to be incorrect, but this book offers one a lot to think about and clear explanations of the bases for what can otherwise seem a little outlandish. There is also some wit in places that contributes to heightened readability.
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