‘There is no shortage of words and pages dedicated to how well the body usually works,’ writes biologist Nathan H Lents, in the introduction to Human Errors. ‘This,’ he continues, ‘is not that story.’
Over six chapters Lents takes the reader on a horror house tour of the body, pointing out all the bits that don’t work very well, from broken genes and dangerous lymph nodes to muscles that attach to nothing and numerous pointless bones. If the human body were designed from scratch by an engineer, these are the bits that no one in their right mind would build in such an illogical way. Like any theme park horror house, it’s a thoroughly entertaining ride, crammed full of the bizarre and enlightening and ripe with facts with which to wow future dinner party guests.
Human Errors starts fairly simply. We learn that the human eye is fundamentally flawed because our photoreceptors face the wrong way – away from the light. Our nasal cavities have also got it wrong. The largest, through which mucus drains, are situated above the sinuses which produce the mucus. It means that the thick, sticky substance has to drain upwards, against gravity, and partly explains why humans are so susceptible to colds and sinus infections. ‘What kind of plumber would put a drainage pipe anywhere but at the bottom of a chamber?’ asks Lent.
As the book progresses, the exploration of our errors becomes more detailed. Lents is at pains to communicate just how startlingly inefficient our reproductive system is. Among the many defects he lists, there’s the basic but disastrous fact that human skulls are extremely large, relative to women’s narrow hips. Not only does this result in extreme pain, it also means we are forced to leave the womb prematurely because otherwise we’d get too big to make it out. The reader is invited to compare the trauma of human birth to that of the giraffe or gorilla – animals that barely blink as fairly capable, perky offspring slip out. Add to that the fact that sperm cells can only turn left, making their journey to the egg cell bizarrely laboured, and the unnecessary gap between the ovary and fallopian tube, which can lead to escapee eggs and abdominal pregnancies, and it’s hard not to agree that the human reproductive system is poorly designed.
Lents is at his best when he explains why these flaws exist. Each glitch tells a story about our evolutionary history. Sometimes incomplete adaptation is to blame – the human knee joint never fully adapted to upright walking and many people suffer terrible torn ligaments as a result.
"'In other instances the problems we face are simply the product of evolutions’ limitations. Lents explains that because we have developed in such a haphazard way, through the process of random gene mutations, errors are inevitable"
Natural selection may have resulted in the rapid increase in the size of our brains and craniums for example, but evolution could not so easily transform the reproductive system to keep up with these changes. Hence the nightmare of human birth.
Some lay readers may find parts of Human Errors a bit technical. This is particularly true in the chapter about the human genome. Lents offers a ‘recap’ of human genetics but assumes a degree of existing knowledge, perhaps overestimating most people’s ability to recall GCSE biology. Nevertheless it’s still possible to get the gist of the chapter (our DNA is chock full of faulty genes and broken chromosomes) even if some of the detail induces a slight headache (probably due to some sort of design flaw).
Considering this is a book about human failings, it is, for the most part, surprisingly optimistic. There’s something comforting about the fact there is a reason for many of our defects. Lents says that most of the things we have to put up with are a byproduct of the way our species has adapted so successfully. Even cancer is described as an inevitable side effect of cell division, a process that is essential for human survival.
Human Errors finishes by turning to the brain. Lents is keen not to cause offence. He reassures us, as he does throughout, that the brain is remarkable (perhaps for fear of creating a cohort of hypochondriacs among his readers). Nevertheless, like everything else, it too is littered with flaws. Having analysed the way our brain plays tricks on us, warping memories, falling for optical illusions and encouraging reckless behaviour, Lents finally turns to the most dangerous human trait of all – superior intelligence.
Of course, our intelligence has allowed us to solve many human problems with technology, rather than relying on the clumsy march of evolution. But as resulting environmental damage looks set to destroy us, Lents asks: ‘Will our advanced intelligence prove to be our biggest asset or our biggest flaw?’ Though he can’t possibly answer this question, the reader is left with the feeling that Lents believes human ingenuity will see us safely through the other side. Considering how knowledgeable he is about human errors, it’s a comforting conclusion.