Wednesday, October 16, 2013

Review: The Story of The Human Body

The Story Of The Human Body is written by evolutionary biologist and Harvard Professor Daniel Lieberman. It's not just a boring history of how your various body parts evolved, but it's also an exploration about how mismatch diseases come about: diseases caused by the mismatch between your relatively old genes and the relatively unusual state of civilization today.

Midway through the book (page 173), there's a list of mismatch diseases that hold a few surprises even for me. For instance, apnea, ADHD, OCD, and chronic constipation are all considered to be mismatch diseases. I'm very familiar with Apnea, and I was surprised to find it on this list. The explanation is surprising: if you grew up on relatively soft processed or cooked food, you didn't have to chew very much or very hard, so your jaw ends up being a bit too small, which is one of the conditions that causes apnea. Lieberman suggests allowing kids to chew gum a lot as a way to help correct this deficiency, and I wonder if Singapore's ban on chewing gum could contribute to a rise in the number of children who end up with sleep apnea in the future as a result.

Which brings me to another interesting point about this book. Because mismatch diseases have long lead times and are caused by conditions in which the child grows up in, but the disease itself doesn't show up until in late adulthood, this book also doubles as a parenting manual of things that you as a parent should do, but might not have realized are important. For instance, he suggests letting kids run around in bare feet as much as possible to prevent future incidences of flat feet. This goes against the norms of civilized society, and parents should take note. Other little tit-bits from this book:

  • Growing up in a hot environment will cause your child to develop more sweat glands. This may or may not be a good thing, depending on your point of view.
  • Baby fat is not necessarily benign: even if the kid grows out of it, being fat at a young age causes your body to have more visceral fat cells, which can lead to being more easily fat as an adult.
  • Myopia could be caused by spending too much time indoors, and insufficient variety of visual stimuli. Having a wide variety of visual stimulus is important for normal vision.
  • If your kids get antibiotics, it might be necessary to follow up with a dose of probiotics to help the stomach flora return to normal.
If you don't have kids, there are lots of other fascinating topics that are relevant to you:

  • Sitting is very bad for you.
  • Human beings are basically the fattest primates around, but there are good reasons why.
  • Why do men get prostate cancer?
  • Why do you tend to get back pain as you age?
These questions all have lots of fun answers in Lieberman's book, plus a huge dose of evolutionary history which explains why if agriculture was such a hard life compared to being a hunter-gatherer, humans adopted it anyway.

Lieberman ties off the book with a bunch of policy suggestions as to how to prevent many of the mismatch diseases he describes. I have a very pessimistic outlook on those suggestions, as the long feedback cycle (40 years or so before diabetes begins to show up) ensures that much like global climate change, there's no real incentive for government to do anything about it.

I thoroughly enjoyed this book and found it incredibly informative. It's very likely to be the best book I've read all year. Highly recommended.
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