Nathan H. Lents

Human Errors examines parts of the human body that are flawed, don't make sense, or otherwise just don't work. The author contends that many of these glitches are unique to humanity. Most animals, for example, do not routinely suffer common colds nor do they need to eat a balanced diet because their bodies can produces the vitamins they need whereas humans can only acquire them through food. This makes sense from an evolutionary perspective as the random mutations that lead to evolution can be very messy. Some things that aren't necessary - like extra bones - cause no harm so there's no pressure to change them while other more dangerous afflictions affect people after the age of reproduction. I found this an interesting book although Lents' writing style needs some polishing. He tends to write his paragraphs as lists of trivia and is repetitive in his phrasing. Nevertheless it is an interesting look at human physiology and evolution.

Favorite Passages:
Because many of the bones of the ankle do not move relative to one another, they would function better as a single, fused structure, their ligaments replaced with solid bone. Thus simplified, the ankle would be much stronger, and many of their current points of potential strain would be eliminated. There is a reason that twisted and sprained ankles are so common: the skeletal design of the ankle is a hodgepodge of parts that can do nothing except malfunction.


Human anatomy is beautiful, no doubt about it. We are very well adapted to our environment, but we are not perfectly adapted. Little imperfections exist. It’s possible that, if our ancestors had lived the hunter-gatherer life for a longer time before moving into the modern era of vaccines and surgery, evolution would have continued to perfect human anatomy. However, that environment, like all environments, was so dynamic that evolution would simply have substituted our current imperfections for others. Evolution is a continual process—never quite complete. Evolution and adaptation are more like running on a treadmill than running on a track: we must keep adapting in order to avoid extinction, but it can feel like we never really get anywhere.


Humans have more dietary requirements than almost any other animal in the world. Our bodies fail to make many of the things that other animals’ do. Since we don’t make certain necessary nutrients, we have to consume them in our diet or we die.


No matter how it evolved, reduced birth spacing with high infant mortality is incredibly poor planning by whatever force designed our species’ reproductive system. That shouldn’t surprise us, however, because evolution doesn’t make plans. It’s random, sloppy, imprecise—and heartless.


In fact, of all the organ systems and physiology in the human body, the reproductive system is the most problematic—the most likely not to work. This is especially odd given how important reproduction is for, you know, the survival and success of the species. And it is especially humiliating when you consider that many of these problems are either nonexistent or at least far less common in other animals.


But humans persevered despite these flaws. As we did for our other flaws, we used our big brains to create fixes to circumvent these evolutionary problems. In a way, rather than waiting for nature to do it, we took charge of our own evolutionary destiny. Our creative thinking and collaborative social living helped us scrape by during the earliest years of our species, and then the emergence of language allowed us to accumulate wisdom through the ages and teach the clever tricks to our children. And who among us are the repositories of all that accumulated social knowledge? The menopausal matriarchs we call grandmas.


Stop and think for a second about how ridiculous allergies are. Some people’s bodies go so crazy over a bee sting that they die. The bee stings don’t kill them; their immune systems do. Even if bee stings were truly dangerous (which they’re not), suicide still seems like an overreaction. Because of hypersensitive allergies, some people’s immune systems are like ticking time bombs. The biggest health dangers they’ll ever face in life is right inside them.


There are two reasons why cancer is so stubborn. First, as Father Mohrman points out, cancer is not a foreign invader; it is our own cells gone wrong, and so drugs that fight cancer cells while sparing normal cells are hard to come by. Second, cancer is progressive—and usually aggressively so. Cancer cells are constantly mutating, which means that it is not the same disease over time; rather, it grows, morphs, invades, and ultimately spreads all over the body. A treatment that works at first will fail eventually. If a tumor contains ten million cells and doctors kill 99.9 percent of them with radiation and chemotherapy, there are still plenty left to regrow the tumor—and it will be even more aggressive as well as resistant to whatever was used to shrink it originally.


Those who survive and reproduce well will leave more offspring than those who do not. It’s hard to imagine life working any other way on another planet, despite how different everything (and everyone) might appear on the surface. However, never have we seen—and never, alas, could we predict—the evolution of disciplined self-control, long-range foresight, rampant selflessness, generous self-sacrifice, or even something as simple as willpower. Evolution has never shown an ability to plan ahead more than a generation or two.… (meer)