In Voltaire’s “Candide”, the protagonist’s servant asks his master to explain the meaning of optimism. To which his master replies: “It is the mania to insist on the fact that all is well when all is not well.” There is perhaps no more perfect description of the human condition, as all is clearly not going well. How is it possible? From the moment of our creation, a silent biological clock begins the countdown to the end of our existence. Our genome manages to mutate into a set of potential pathologies, each capable of corrupting and unraveling us. We respond with attempts to heal and heal, to correct the inherent flaws and brilliant imperfections that make us so overwhelmingly human.

In the entertaining “Evolution Gone Wrong: The Curious Reasons Why Our Bodies Work (or Don’t)” by Alex Bezzerides, the author’s quest is to determine the origins of “the aches and pains of the masses and why they occur “- and not the causes of our diseases but those of evolution. The explanation, concludes Bezzerides, can be found in our anatomical shortcomings – “trade-offs” made in our continuing evolutionary history. The result is that even healthy bodies are operating at the limit of acceptable performance, while also being prone to fail in predictable ways.

The catalog of human fallibilities that Mr. Bezzerides collects begins with an account of our suboptimal dentition. For many people, the manual display of 32 carefully arranged teeth, systematically configured to produce the perfect Hollywood smile, is optimistic at best and more often than not fictional. Reality more generally involves a procession of braces, extractions and eccentric protrusions. So why don’t our teeth fit in our mouths?

The answer, says Bezzerides, is that four million years ago our ancestors went from a diet of fruits and leaves to a diet of grasses and sedges. Their molars swelled to gargantuan proportions, which was not a problem at first, as their substantial jaws easily accommodated the newly enlarged teeth. But as humans controlled fire, learned to cook, became cooperative, and developed hunting techniques and an associated arsenal of cutting implements, the requirement for sturdy dentition diminished. We were nonetheless stuck with the legacy of a “mouth full of big teeth”. The size of the jaw and teeth then began to decrease, but the distinct genetic programs controlling each led to a disconnect between their relative rates of reduction. While the human jaw enthusiastically embraced its “great narrowing,” the reduction in tooth size struggled to keep up. Hence the modern tooth-jaw inadequacy.

Our imperfectly functioning eyes similarly suffer from the stresses imposed by our distant evolutionary history. More than half of European adults have visual defects, while a quarter of American children need vision correction. The problem, according to Bezzerides, is that the eyes of our vertebrate ancestors evolved to function underwater. When vertebrates first settled on earth 375 million years ago, their eyes had already existed for over 100 million years. The reconfiguration of such established biological material was no small feat, leaving us with myopia and a range of quirks, including having to blink up to 14,000 times a day while deploying a can of Coke full of lubricating tears.