Human Errors

by Nathan H. Lents

  If someone makes it to the age of twenty-five without picking up a cigarette, he has an almost zero chance of starting after that. The label of nonsmoker is pretty firmly established even by the time a person hits twenty-one. As people mature, they become far too wise to start a habit as foolish as smoking. Especially since the first try is so awful—who the hell would be irrational enough to keep at it? Well, I was, and so are millions of other kids. So the question is not who, but why?

  The key to understanding risky behaviors lies in another basic fact: They are more prevalent not only in young people, but also in males. Young adult males are the most dangerous demographic of the population, and the reason for that is even stupider than the risky behaviors themselves: they do stupid things in order to impress people.

  Young people, particularly but not exclusively males, take insane risks in order to advertise their “fitness.” This does not necessarily mean displaying physical prowess, although it can certainly be that. The term fitness display comes from the study of animal behavior and refers to ways that animals communicate to potential mates, as well as potential rivals, that they are forces to be reckoned with. It’s a way of saying, I am so powerful that I can do this dangerous thing and still come out okay.

  If we use the analogy of smoking, the coded message is I am so healthy that I can survive doing what we all know is incredibly unhealthy. If young men were taking these risks purely for their own thrill, they would take them when they were alone, but they don’t (until, in the case of cigarettes, they become addicted to the nicotine). The crazy behavior is always done in full view. The larger the audience, the better.

  Displays of fitness have a long evolutionary history, and there are many different types, but for our purposes, the ones that matter fall into a specific category that biologists call “costly signals.” Costly signals are responsible for some of the more conspicuous examples of sexual selection found in nature. For instance, the enormous tail of the peacock and the bulky antlers of the stag serve no other purpose than attracting mates. And they are costly; it burns many calories to carry them, and they reduce the animals’ speed and mobility. While it is true that some horned mammals use their horns to fight among themselves, many never or rarely do so. The antlers and the tails are mostly for display, to show the females how strong they are. How does a huge tail show off strength? Well, you try lugging that enormous thing around everywhere you go without starving to death or getting killed.

  The handicap principle states that sexual selection sometimes leads to the evolution of ridiculous impediments to survival that exist purely so the male can display feats of strength. These examples of runaway selection are hardly good for the overall health and vitality of the species, yet those enormous antlers that are purely for show? They work! Female deer are strongly attracted to large and elaborate antlers. Size matters. Same for the tail of the peacock. Peahens dig it.

  Applying the handicap principle to behavior is tricky, and applying it to humans is trickier still. However, there is solid evidence for doing so. Studies have confirmed that young females experience stronger sexual attraction to males who display risky behaviors, particularly those involving feats of physical strength. Young women will score the same male as more attractive when they see him playing football than when they see him playing the piano.

  Even more telling is the fact that males are impressed by their fellow males when they see them taking risks. Doing things like drag racing, cliff diving, and smoking cigarettes helps a young man earn and keep male friends. In evolutionary terms, these are male-male alliances, and they can prove very valuable in securing a prized place in the dominance hierarchy of social species up to and including humans. And if you’re a male, the higher you are in your dominance hierarchy, the greater your chances of reproductive success. We humans like to think we’re above all that, but I suspect everything in this section sounds familiar to anyone who survived high school.

  By contrast, young males tend to be more sexually attracted to females who take fewer risks. This may help explain why males are drawn to taking risks more than females are—there is a potential payoff for them but not for females. This also supports the notion that, in mammals, individual males are fairly expendable, while females are a limiting factor for the survival and success of the species. In this view, each female is precious, and males are generally drawn to females who show signs of caution and care and, thus, will be able to ensure the survival of their children. Females, however, worry less about caution in their mates and instead want good genes for their offspring.

  This is a dramatically overgeneralized view, of course, but like the clichés about age and risk-aversion, it has some grounding in truth. It’s basically a truism that the jocks get the girls in high school while the geeks get passed over, even though the latter are probably more likely to experience real-world success later in life. By that time, the tables get turned, but it’s too late for many women and men because they’re done reproducing. And while it might be tempting to think that the recent increase in the age of first reproduction among humans will reduce costly displays of fitness among young men (and make smart, sensitive young men more attractive to their peers), this is unlikely to have any quick impact. An evolutionary transformation like that would require a genetic difference between risk-takers and safe players, followed by many generations of selective pressure. Absent those factors, humans can count on adolescent boys doing stupid things for some time to come.

  An important implication of this bug in our brains is that much of the public-awareness programming aimed at reducing rates of smoking, drinking, drug use, and other risky behaviors may be totally backward in its approach. While explaining the risks of drugs to a high school student might seem like a logical way to dissuade him from trying them, it probably has the opposite effect. Explaining that drugs are risky could make them more attractive to kids, especially young boys. There is wisdom, indeed, behind another old saw: There is no better way to raise interest in something than by banning it. In the primate brains of young boys, if drugs are dangerous and illegal, the people who try them must be really strong and brave. Could there be a clearer cognitive flaw than that?

  Coda: Saints and Sinners

  How humans became so much more intelligent than our closest relatives in such a short time is one of the biggest mysteries of evolution. While it’s obvious that high intelligence has survival advantages and would thus be favored by natural selection, it is actually a fairly improbable feature for a species to evolve.

  First of all, evolving to be smarter requires a fairly ordered progression of a lot of mutations, such as those allowing the expansion of the cranium, the growth of the brain itself, greater interconnectedness of brain areas, and so on. Second, at least in mammals, it also requires changes in female reproductive anatomy to accommodate larger craniums during childbirth. Third, brains are extremely energy-hungry and thus place intense demands on organisms to acquire enough calories to support them. For example, the human brain consumes about 20 percent of the body’s daily energy expenditures, more than any other single organ. The fact that so many long-persisting lineages, such as sharks, horseshoe crabs, and turtles, never bothered to evolve big brains underscores how costly and improbable it is.

  But big and smart brains did evolve in humans, despite the costs and anatomical constraints. Therefore, this would seem to be a triumph of good design, hardly a defect. But a closer look reveals that our large and powerful brains may actually be the biggest flaw of all.

  Most anthropologists agree that the initial phase of the expansion of human intelligence took place over the first four or five million years of our species’ divergence from the chimp lineage and was marked by the shift to larger and more intricately cooperative social groups. As our ancestors shifted to a bipedal posture and eked out a living at the borderlands of dense rainforests and grassy savannas, they began to creatively master a broader range of survival skills. They needed expanded cognitive
abilities to perform these complex skills but also to learn them. Through the human lineage, our species gradually made a transition from preprogrammed behaviors and skills to learned ones. Much of the learning took place socially, with one individual teaching another. Thus, skills and social interactions were linked and both evolved together, pushing the human brain toward ever-greater abilities.

  Our ancestors’ cranial capacities expanded gradually for most of the past five million years but then accelerated in the last million and a half years. This dramatic acceleration may reflect the development of new, antisocial competitive strategies.

  As upright posture freed our ancestors’ hands to carry things and make tools, and as growing brains and larger groups facilitated social learning, humans found themselves in the perfect environment for the emergence of more complex forms of communication and cooperation. Cooperation requires perspective-taking and empathy; in order to really cooperate with you, I must be able to imagine how events will unfold from your point of view. In order for people to work effectively in teams, each member of a group must have some appreciation for what the other members in the group are seeing, thinking, and feeling. Our ancestors took cooperation and sociality to dramatic new heights, and their powerful intelligence played a key role in that. Until . . .

  About a million and a half years ago, brain expansion in our ancestral lineage suddenly accelerated dramatically. Human brains have grown more than twice as much over the past one million years than they did in the five million years before that. What happened to facilitate that rapid change?

  Recent studies have indicated that the rapid acceleration of brain growth in our ancestors was likely due to a switch to more competitive strategies for survival. At this time, there were several species of hominids vying for similar habitats and resources. In addition, even within the same species, different social groups would compete with one another when their territories overlapped.

  Competition among groups of animals is nothing new, of course, but our ancestors approached this competition with dramatic new cognitive abilities. This is where things get very dark.

  Humans engage in competitive behaviors that are downright Machiavellian. We manipulate, deceive, entrap, and terrorize. To do this, we use many of the same skills that serve us well for cooperation: perspective-taking, predicting another person’s next move, and so on. In other words, throughout our evolutionary history, we began using our impressive cognitive powers for good, but then we turned to the dark side. And, like Anakin Skywalker becoming Darth Vader, that’s when we grew really powerful.

  To see the evolutionary legacy of this adaptation, look no further than today’s headlines. Humans are capable of unspeakable violence toward one another. We plot against one another with ruthless cunning and complete disregard for others’ suffering. The surprising part is that our ancestors didn’t sacrifice their cooperative, pro-social, even altruistic nature in the process of becoming so ruthless. They kept both sides—becoming a species of Dr. Jekylls and Mr. Hydes.

  The duality of human nature is the hallmark of the human experience. We can switch from boundless love and great self-sacrifice to cold-blooded murder, even genocide, in a heartbeat. Just a few generations ago, the United States of America and many other countries were populated by men who were loving fathers and doting husbands and who made their fortunes by brutally enslaving other human beings. By all accounts, Adolf Hitler was a generous and gentle partner to Eva Braun even as he ordered the senseless slaughter of millions.

  How can such unspeakable monstrosity and genuine affection coexist in the same species, let alone the same individual? Because evolution rewarded those of our ancestors who could nimbly switch between cooperation and competition when the conditions suited them. We evolved to be highly social, collaborative, and altruistic but also ruthless, calculating, and heartless. It is this latter set of traits that seemed to facilitate the evolution of our great big brains. So the next time you praise someone’s intelligence, stop to think about what—or, rather, who—had to be sacrificed in order for her to get that smart.

  Epilogue: The Future of Humanity

  Why humans are still evolving, despite what you may have heard; why all civilizations, including our own, may be destined to implode and rebuild in an endless cycle; why we may live indefinitely healthy lives in the not-too-distant future; why technological advancement has both raised the possibility of our self-destruction and provided us with the means to avoid it; and more

  This book has surveyed only a fraction of the defects in the human body. We have many other mental biases, countless additional problems with our DNA, and lots of other useless (or needlessly complex or breakable) body parts among myriad sundry flaws not mentioned here. Any book attempting to cover all human imperfections would need to be much, much bigger than this one—and much more expensive. You’re welcome.

  That said, our many flaws should not make us feel bad about ourselves. After all, evolution works by random mutation and survival of the fittest, not of the perfect. Such a haphazard approach to life could never produce perfection. Every species is a balancing act of positives and negatives. Great as humans are, we are no exception.

  But when it comes to imperfections, the human story is unique. We do seem to be more flawed than other animals, and the reasons why, paradoxically, come from adaptations that really should have been improvements. For example, the reason we must pursue such a diverse diet in order to stay healthy while other animals can survive on a single type of food is that our ancestors were able to break free from the monotony of subsisting on staples and use their great cognitive powers to forage, hunt, gather, dig, and otherwise seek nutrition from every conceivable food source across multiple habitats. That sounds like a good thing, but the problem is that, as their minds grew powerful, their bodies grew lazy. Basking in the variety of their rich diets, their bodies simply quit bothering to make many nutrients that they previously did. This forced our ancestors to switch from being able to enjoy a rich diet to requiring a rich diet in order to survive. That’s an unfortunate switch. What was clearly an advantage to start with—being voracious omnivores—became a limitation.

  This same logic applies broadly to human anatomy and physiology. Our species’ physical form is the result of compromises forged by evolution as humans became the ultimate generalists. There are species that can run faster, climb higher, dig deeper, or hit harder, but humans are special because we can run, climb, dig, and hit. The phrase jack of all trades, master of none fits us perfectly. If life on earth were like the Olympic Games, the only event that humans would ever win is the decathlon. (Unless chess became an Olympic sport.)

  Other problems we experience with our bodies are due to the many differences between the environment our ancestors evolved in and the environment humans now live in. Those differences lead to so-called mismatch diseases, such as obesity, atherosclerosis, type 2 diabetes, and many other disorders. Much of these problems of environmental mismatch stem from differences between our ancestors’ diet and ours, but another big difference between how our ancestors lived in the early Stone Age and how we live now has to do with technology. Because technology has allowed us to move beyond the physical limitations of our bodies, it would seem like a purely advantageous phenomenon. However, the less we rely on our bodies, the less they are pressed to adapt and evolve. Now that we are solving so many of our problems with technology instead of biology, it’s no surprise that our bodies are not exactly in tiptop shape.

  Of course, humans are not the only species to use technology. For our purposes, I’m defining technology as methods, systems, or devices crafted for their utility in performing a task, and by this broad definition, many animals make use of technology. Macaques use rocks to crack nuts, and chimpanzees shape sticks to use in their hunt for termites, to give a couple of examples. In our species’ case, early humans used simple stone tools. But unlike macaques and chimps, who are still using the same tools that they have wielded for milli
ons of years, humans’ invention of stone tools ushered in a new kind of evolution that has set us apart from every other animal under the sun and for which there is no turning back: cultural evolution.

  Cultural evolution refers to the social practices, knowledge, and even languages that are passed on through the generations. While animals certainly learn some things from one another, humans have taken the concept of culture to the extreme. Almost everything we do and experience in our lives is the result of culture, and this has been the case for quite a long time. Once modern humans began sharpening rocks, building dwellings, and, eventually, planting crops, they began to succeed or fail based on cultural features rather than biological ones.

  In a sense, we have taken charge of our own evolution, but are we really in control? As technology and culture continue to advance, what changes are in store for us? Now that we understand how our biology and culture evolved, are we able to manipulate them at will and therefore shape human destiny in a deliberate and intentional way? Or will we continue to plow ahead in the same random, haphazard manner that we have for the past seven million years? In short, what does the future hold for our species?

  Are We Done Evolving?

  Some high-profile people in the scientific community, including Sir David Attenborough, have asserted that humans have developed so far in our civilization and technology that we have fully escaped the forces of evolution. We are no longer evolving, they say, and our species will remain more or less the same in its biology, absent any intentional tweaks that we accomplish.