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Monday, February 21, 2022

Review: Evolution Gone Wrong

 Evolution Gone Wrong is the book about humanity's poorly designed bodies.  This is such a good genre of books, that I could read multiple books like this and not get tired of it. It's the perverse side of the usual self-congratulatory books about how well designed our bodies are.

The book covers diverse topics such as the shape of our jaw and why we have too many teeth for the size of our jaws (answer: the evolutionary path of teeth and jaws are different, and post-agricultural revolution jaws are smaller, since cooked food doesn't require as much chewing and jaw strengthening exercises so our jaws continued shrinking). It covers why humans choke on food (the larynx is lowered so the humans can speak to each other), and myopia:

Children who spend greater chunks of their day outside have a lesser risk of developing myopia than children who spend their days inside. It doesn’t matter how they spend their time outside. The outdoorsy kids in the studies spent as much total time on screens as the indoorsy kids. They didn’t have to be kicking a soccer ball or climbing a tree. Even if they were playing around on their phones, as long as they were doing it outside, they were less likely to become myopic. It is a shocking result given the total buy-in to the eye-strain hypothesis. (kindle loc 865)

What's interesting is the study on sleep, indicating that even Chimpanzies make the bed:

 They sampled 1,844 chimpanzee night beds (take a second to appreciate that large sample size) and discovered that chimps used the same type of tree to build a nest in 73.6% of cases. Interestingly, the preferred tree made up only 9.6% of the trees in the forest. In other words, the sleepy chimps were not grabbing branches at random and knocking out shoddy, makeshift beds. They were being selective about their mattress materials. The sleep researchers also analyzed the properties of the preferred trees. In the article they published in the journal PLOS ONE, they note that the most coveted type of tree was a species of ironwood that “was the stiffest and had the greatest bending strength” of all the options for bedding materials available to the chimps. So chimps go for mattresses with some give, but ones that are also stable and firm. (kindle loc 2380)

One interesting conclusion is that stiff beds don't actually do as well as medium beds for providing good sleep, which is counter intuitive. The author spends a half chapter pointing out that you can tell which parts of the bodies are maladapted for modern living by looking at medical schools. For instance, dentists don't go to medical school because the demand is so high that society puts dentists directly to dental school. The same goes for podiatrists.

 Any anatomical area that needs its own entire branch on the medical tree clearly troubles a great number of people, as we saw with all the problems covered in the first section of the book. (kindle loc 1714)

The final part of the book covers our reproductive dysfunction:

 Dogon women experience, on average, roughly 100 total menstrual cycles in their lifetimes (the mean in the study was 109 and the median was 94) and birth, on average, 8.6 children. Those numbers are strikingly different from what women experience who are not practicing natural fertility. Strassmann estimates, based on data from other researchers, that it is not unusual for modern American women to go through as many as 400 menstrual cycles in their lifetimes. (kindle loc 2568)

An interesting section covers why women menstruate at all. For one thing, the relationship between fetus and the woman's body isn't a completely friendly one:

 Horse and pig fetuses, for example, do not burrow very aggressively into the womb. The membranes surrounding the fetus are several layers of tissue removed from the maternal blood supply. There is still maternal–fetal conflict in those species, but not the same degree of conflict seen in species where the fetus digs in further. Dogs and cats are somewhere in the middle. Their fetal tissues start to invade the maternal tissues but are still distanced somewhat from the maternal blood vessels. In the most aggressive version of placentation, the fetus roots in, like a mole into dirt, and snuggles right up against the blood vessels of the mother. You can probably guess which type of fetuses humans ended up with. We got the uberaggressive model. And again, we see the comparative approach pay off in solving this riddle of why SD evolved. The animals that exhibit SD and menstruation are also the ones with the most invasive fetuses. Some scientists think SD evolved as a preemptive degree of protection against a hyperinvasive fetus. The logic goes that a woman gets ahead of the game and builds in some extra protection before the vampire-fetus arrives so that her unborn child does not completely suck her dry. After all, if you know a vampire is coming to your quaint, remote village, it makes sense to start beefing up the defenses of the village before the little bloodsucker gets there. Get the garlic planted, the stakes sharpened, and the mirrors shined in preparation. (kindle loc 2751)

 There's even a great section on why Asians are more prone to diabetes at the same body weight compared to European-Americans.

All in all, it's a fun book, written with humor, and keeps you engaged while reading. Recommended!

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