Review: Human Errors

Human Errors has one of the best premises I'd ever seen for a science book. The idea is that there are plenty of books extolling the wonders of the human body, how well designed it is, how delicately controlled it is, etc. But this is the book that focuses on the bugs in the design of the human body. And boy there are many bugs (as anyone over the age of 40 can attest). For instance, I've always contended that the human nose/sinus system is the worst design anyone can come up with, and this book confirms that:

There are a variety of reasons for why we’re so susceptible to sinus infections, but one of them is that the mucous drainage system is not particularly well designed. Specifically, one of the important drainage-collection pipes is installed near the top of the largest pair of cavities, the maxillary sinuses, located underneath the upper cheeks. Putting the drainage-collection point high within these sinuses is not a good idea because of this pesky thing called gravity. While the sinuses behind the forehead and around the eyes can drain downward, the largest and lowest two cavities must drain upward. Sure, there are cilia to help propel the mucus up, but wouldn’t it be easier to have the drainage below the sinuses rather than above them? What kind of plumber would put a drainpipe anywhere but at the bottom of a chamber? (Pg. 10)

Indeed, the book confirms that other mammals like dogs, horses, and cats simply just don't suffer from the constant respiratory colds that humans do, because their sinuses drain correctly. Our heritage is due to the flattening of our noses (probably a result of sexual selection).

Similarly, nearly every athlete you've met who's an active runner, tennis player, basketball player, or soccer player will have had their knees go wrong. The knee is another badly designed body part:

 In quadrupeds, the strain of running and jumping is spread among four limbs, and the limb muscles absorb most of it. Once our ancestors transitioned to bipedalism, however, the strain was spread over two legs instead of four. This was too much for the muscles by themselves, so our bodies recruited the leg bones to help with the strain. The result was that human legs became straightened so that the bones, rather than the muscles, could bear most of the impact. Compare a standing human with a standing ape: a human’s legs are fairly straight, while an ape’s legs are bowlegged and usually bent. This straight-leg arrangement works out okay for normal walking and running. But for sudden shifts in direction or momentum—when you’re running and then stop short or when you make a sharp turn at high speed—the knees must bear the force of this sudden, intense strain. Sometimes, the ACL is simply not strong enough to hold the leg bones together as they twist or pull away from each other, and it tears. (Pg. 23)

 I book even came up with some human defects that I didn't thin about. Consider the frequent exhortation to eat a variety of foods in order to get all the micro and macro nutrients that we need. Why the heck do we need so many crazy micro-nutrients?

Some people’s diets don’t give them everything they need, and even people who get everything they need can’t always absorb it properly. So sometimes, we need a little boost. That’s why we’re always being told to drink milk, for instance; it gives us the calcium that we need but can’t produce in sufficient quantities ourselves. Now compare our demanding diet with the diet of the cows that produce that milk. Cows can survive on pretty much nothing but grass. They live long and perfectly healthy lives and produce delicious milk and rich meat. How can these cows thrive without a delicate mix of legumes, fruits, fiber, meat, and dairy like humans are told to eat? Forget cows; look at your own cats or dogs. Consider how simple their diets are. Most dog food is nothing more than meat and rice. No vegetables. No fruits. No supplemental vitamins. Dogs do just fine on this diet and, if not overfed, can live long and healthy lives. How do these animals do it? Simple: they are better designed for eating. (Pg. 36)

The book goes on to describe how our vitamin C generation gene is literally broken. It's in our genome, but some mutation disabled it ages ago so now we can't make our own vitamin C.  Similarly, we can't extract iron from vegetables easily, and worse, our intestinal system is so badly designed that our large intestines generate vitamin B12, but only the small intestines can absorb it, so all the vitamin B12 our body creates gets dumped out with our stools. Take that, intelligent design!

I spent the first 50 pages of the book highlighting one great passage after another, and fully expected to give the book nothing less than 5 stars by the time I was done reading it, but after the first 2-3 chapters the book sort of ran into a brick wall. Part of it is that my recent reading of Sex at Dawn has revolutionized my view of human reproduction, so his inveighing of our "lousy" reproduction system rings false to me. (Human fertility simply would not have been an issue in the tribal hunter-gatherer lifestyle, though obviously death from childbirth and infant mortality would have been a big issue, but that's a property we share with all animal life!) Similarly, his analysis of our lifestyle diseases like obesity and cancer again don't seem like design flaws rather than the inevitable trade-off evolution had to make between reproductive fitness and long life.

By the time we get to the human brain defects (well worn in Daniel Kahneman's Thinking Fast and Slow and obviously not covered as well in this book), I was only reading hoping to get a few more gems out of it, and didn't get it.

In any case, I felt like the first half of the book was awesome, and covered material not covered anywhere else, but the second half of the book was full of padding and material better covered elsewhere. Nevertheless, the book overall is worth reading (especially if you haven't read as widely as I have about prospect theory), and comes recommended.