The mapping of the genomes of our closest living animal relatives can help unravel the mysteries of the human genome. It is critical to complement the genetic data with information about cognitive and other traits of nonhuman primates. Traits that turn out to be unique to humans are likely dependent on those aspects of the genome—and the nervous system—that are unique. Knowledge of the gap helps narrow down the search space for identifying the neurological and genetic bases of these traits.
By the same token, we can take advantage of knowledge about what we share with some of our closest relatives. For instance, consider the finding that humans and great apes share a capacity for mirror self-recognition and stage 6b object permanence, whereas small apes do not (see Chapter 3). Given the close relation between these species, the trait in great apes is most likely a homology—that is, we inherited it from a common ancestor that evolved it between eighteen and fourteen million years ago. A homology entails that the trait is driven by a similar inherited neuro-cognitive and genetic foundation. In other words, it relies on a basis that humans and great apes share, and that we do not share with gibbons. To identify what critical changes make the trait possible, then, one can focus research on those aspects of the brain or genome that great apes and humans have in common but that they do not share with small apes.
Evolutionary perspectives are increasingly proving useful in diverse areas of psychological inquiry. Though evolutionary psychology textbooks still often feature little discussion of our closest living animal relatives or even of our extinct hominin relatives, the material covered in this book illustrates how critical they are. A careful appreciation of the making of the gap, I would argue, is essential for a truly evolutionary perspective on the human mind. Perhaps one day Darwin’s prediction that psychology will be based on a new foundation may yet be fulfilled.
WHAT ABOUT THE FUTURE OF the gap itself? There are three obvious possibilities: the gap could decrease, increase, or remain the same. The view that the gap is stable may derive from a belief that humans are no longer evolving—a perspective quite widely held. Could it be that cultural and technological advances mean biological evolution no longer matters to us? We have become so powerful in creating artificial worlds that we primarily seem to adapt the environment to us rather than the other way around. Modern medicine increasingly circumvents natural selection, and our global interconnectedness means there are no longer many isolated pockets in which human evolution can diverge. Has the evolution of our minds stopped?
On a moment’s reflection this scenario seems rather unlikely, and even reeks of arrogance, as it seems to imply that we are the final product—the height and endpoint of evolutionary achievement. I find it difficult to believe that after four billion years of life forms changing on the planet, it all comes down to the perfection that is you and me. Given our past, it seems more likely that we are another segment in the long chain of evolutionary change. Tens of thousands of generations from now, if we manage to not go extinct, our descendants will look back at us as early humans. In fact, there is evidence that even over short time frames natural selection is effective in bringing about genetic changes in human populations. Furthermore, natural or human-made disasters can create isolation rapidly—as could human success: just think of the possibility of humans eventually populating other planets. Those who do go extraterrestrial may quickly find themselves isolated and available for separate evolutionary trajectories. In sum, it is highly unlikely that evolution will stop with us.
What, then, is the trajectory of the evolution of the human mind? Some data suggest that over the last ten thousand to fifteen thousand years, as population density increased, brain sizes decreased. Given associations between brain size and IQ, this may reflect a decline in mental ability over the time we gained most of our amazing technological powers. Potential reasons for this decrease are changes in nutrition and climate, as well as the possibility that our societies, with extensive division of labor and social safety nets, enable the less mentally endowed to survive where in the past they would not have reproduced. Many of us get by without having the basic skills of hunting and gathering that had been essential for our forebears. Perhaps as technology does more and more of the hard work for us, our artificial world will put ever less demand on our minds. It is imaginable that in the future we will all sit in our lounge chairs and play in virtual reality. Is it possible that our mental capacities are dropping and the gap will become smaller?
It seems unlikely that our minds will dumb down dramatically as long as humans are needed to design and maintain these artificial systems. However, the forces of natural selection on humans today are puzzling. The rich, successful, powerful, beautiful, and well-educated people seem to breed less, not more, than most of the rest of us. In other words, they appear to leave fewer copies of their genes in the next generation than those not blessed with these seemingly highly advantageous attributes. One may therefore worry humanity will slowly lose its edge and the gap eventually gets smaller as a result.
It is also possible, of course, that we cut short our own success story more dramatically. In addition to radically changing the environment, our arms races have resulted in weapons that enable us to annihilate each other many times over. War, terrorism, or mishaps could quickly result in a dramatic unraveling of our civilizations. If we somehow mess it up, our minds may struggle to rebuild, especially as we become ever more dependent on technology. As Einstein warned, “I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.” Countless civilizations have collapsed. In addition to violent conflicts, common causes include habitat destruction, soil and water management problems, overhunting and overfishing, introduction of new species, and overpopulation. As we are increasingly linked into one system, and we face many of those problems on a global scale, it is possible our modern civilization too will collapse one day for similar reasons. A potentially bleak future awaits in which few survive and other creatures are given a chance to close the gap.
A scenario like the one in the 2011 film Rise of the Planet of the Apes, in which we unleash a deadly pandemic while simultaneously enhancing the capacities of apes through biotechnology, is highly unlikely but not entirely out of the question. Genetic engineering has given us radically new powers to influence evolutionary pathways. Advances in biotechnology, such as the capacity to turn any cell into a stem cell and use it to grow body parts or entire organisms, will open up incredible opportunities. It is not far-fetched to assume that we may one day be able to alter brain development and enhance the minds of our closest remaining relatives. Humans are increasingly guiding evolution itself. Some call this “playing God.”
Humans have played God for a long time. At least since the beginnings of agriculture humans have practiced what Darwin called “artificial selection.” We encourage versions of plant and animal life that are useful to us and discourage those that are not. Artificial selection may also have been important in the shaping of our own species. Hitler’s genocides and attempts at breeding a superior race may be the first things to spring to mind, but we socially guided our evolution long before any notions of eugenics. Capital punishment and banishment from social groups not only enforce social norms but select against certain undesirable attributes, such as tendencies to rage violently. Richard Wrangham and Brian Hare have argued that we have domesticated ourselves much as we have domesticated dogs and horses. Domesticated animals are not only less aggressive and more cooperative than their wild counterparts but also typically sport smaller brains. So this proposal is in line with recent human brain size reduction and the overall decline in violence and increase in cooperation that Stephen Pinker argued has characterized recent history.
We have gained some significant new capacities for what we might call “auto-artificial selection.” Contraception is the most obvious, letting us curtail reproduction. Conversely, we can make sperm fertilize eggs in ways other than through sex. We will incr
easingly have the opportunity to deliberately determine not only the number of offspring but also their characteristics, from sex to disease resistance. Many people have understandable reservations about such interference. But imagine if you could make the genetic changes to stop your child from getting cancer, Alzheimer’s, or whatever else has plagued your family tree. It is a small step from preventing disease to influencing the intellectual capacities of offspring or altering the shape of the nose. This direct interference in the genetic makeup of the next generation—“artificial mutation” rather than just artificial selection—may lead to drastic changes as we fast forward tens, hundreds, or thousands of generations into the future. We are increasingly acquiring the power to shape our own evolution, and we may well end up using it to acquire greater mind power.
I predict that the gap will widen. In fact, there are signs it already is widening. Over the past century humans have improved in their average performance on intelligence tests by about 3 percent every decade. Some evidence suggests that brain size, contrary to the trend of the last ten thousand years, may have slightly increased over the last 150 years. We have more nutritious foods and more stimulating education. We bolster our scenario-building minds with ever more refined machines and technologies that allow us to measure, model, and control the world in increasingly powerful ways. Through the internet and other electronic networks we are connecting millions of minds and bringing about an explosive growth in cultural accumulation. Answers to most questions are only a few clicks away. Science is accelerating, and greater knowledge in turn will open doors for the already foreshadowed biological, as well as electronic or chemical, enhancement of human mental powers. We are getting ever smarter—and, one can only hope, wiser.
There is a second way through which we may increase the gap. We could make ourselves appear more special on this planet by reducing the capacities of our closest animal relatives—moving the other side of the chasm. I do not mean we somehow dumb down the apes; I am referring to driving them to extinction. Their demise would turn other species into our closest living relatives, thereby widening the gap. Let’s face it: we are in the process of doing just that. As we have seen, all the great ape species are endangered, and their numbers are primarily declining for one reason: human activity. Whether through habitat destruction, bush-meat consumption, or the pet trade, we are causing the demise of our closest animal relatives, perhaps not entirely unlike what we might have done to our upright-walking hominin relatives in the past.
There are, of course, humans who are desperately trying to stop the extinction of apes, and I encourage you to join them, but the current projections are bleak. In a couple of generations, our descendants might wonder at just how different they are from their closest remaining animal relatives: the monkeys. Apes may join Neanderthals and Paranthropus as half-forgotten creatures of the past. So our descendants may be even more baffled by their own apparent uniqueness (and possibly be distracted by questions about the importance of the fact that monkeys typically have tails whereas humans do not). Let’s make sure they are more enlightened about the nature and origin of the gap. We better protect our tailless ape relatives carefully—for their own sake, as well as for the sake of our children.
We can consider the long-term consequences of our actions. We are the only species on this planet with the foresight capable of plotting a path toward a desirable future. Plan it for the apes. We are beginning to appreciate the drastic consequences our activities have had on Earth, and we can increasingly predict what repercussions our actions will have. So we are burdened with the responsibility of making the right decisions in the present. Humanity has a wondrous potential to cooperatively address impending disasters and to protect our own future as well as the future of our cousins on the other side of the gap. There are reasons to be hopeful. History is not just full of violence and cruelty but also full of heroism, kindness, and prudence. We have overcome many obstacles in the past, and we are better equipped than ever to look ahead and to collectively steer the ship out of troubled waters toward new frontiers.
1Writing appears to have also been invented in other regions: in China, in Central America, and on Easter Island. It is possible that these are entirely independent inventions of script, though any sort of contact with people who write could have given someone an idea.
2Those who continued to pursue a hunter-gatherer lifestyle have increasingly been marginalized. Few cultures have been able to maintain this ancient way of life and only at those locations that were least attractive for farmers.
3Writing systems in other parts of the world may have been invented for other reasons. In the Americas, for instance, concern for time and calendar may have been critical to the early symbols of Olmec and the later full-fledged script of the Mayans. In China the earliest undisputed scripts are divinations on animal bones, though there is some debate about potentially older origins. Little is known about the Easter Island script, Rongorongo, which has not yet been deciphered. Though humans have created many diverse scripts, the neuroscientist Stanislas Dehaene has made the case that they have much in common because of specific constraints on how visual information is encoded in our brains.
4This means that his readers should not need a description, given that they are human themselves, but it also, perhaps inadvertently, points to self-knowledge as something that may set us apart from other animals.
5This need not lead to a wholesale rejection but rather to a refinement of the analysis. Ideally, researchers who argue that their findings show that a trait is not unique should also suggest where the difference lies instead (e.g., the recursive capacities might be limited to a particular domain). Ideally, the new hypothesis explains all that the earlier explained plus the new facts.
6I regularly ask students about their intuitions, and their answers often include the domains discussed here as well as a host of other possibilities. Recently they wrote essays on topics such as adornment, aesthetics, arts, celebrations, complex emotions, dance, democracy, engineering, games, greed, hospitality, humor, law enforcement, mathematics, medicine, music, religion, rituals, schizophrenia, sexual modesty, spirituality, sports, suicide, thirst for knowledge, and warfare. In most of these, to the extent that they are uniquely human at all, the case that the two legs play a major role in carrying our uniqueness can be made. However, in some, such as aesthetics, this is not so clear. Aesthetic projects, of course, may depend on the artist envisioning scenarios and on a drive to get a message across. But the basic notion that some things are more pleasingly aesthetic than others does not really depend on these traits. So there might be something extra here, though it is also possible that other animals have such preferences too. Clearly, a lot more comparative work needs to be done.
7Perhaps this is the place to make one concrete futuristic prediction myself. I suspect that scientists will one day clone Neanderthals and other earlier hominins. I am not sure if I am optimistic or pessimistic about the consequences of this one, but it would be quite interesting.
ACKNOWLEDGMENTS
THIS BOOK HAS BEEN A long time coming. It is the accumulation of much recent work from across a wide range of disciplines. It is also the accumulation of my personal journey of discovery. Since I was a teenager I have wondered why we are the peculiar creatures we are, and much of my research has been ultimately driven by related questions. I kept on collecting pieces of information I saw as part of the larger puzzle until I had enough, I thought, to attempt constructing a coherent picture for more public display. It took more years than anticipated to complete this book, and telling the story ended up involving more self-disclosure than I had anticipated. Please forgive the indulgences.
The efforts of many people went into the writing of this book. First and foremost I want to thank my sounding board and proofreader, the gutsy Christine Dudgeon, who, in the name of science, dives with sharks, takes tissue samples to study their genetics, and makes them vomit to study what they eat. Thank you for your encourag
ement, support, enthusiasm, and love. Chris is my best friend and mother of our wonderful children, Timo and Nina. Our kids have been untiring participants in many an experiment and are the source of tremendous inspiration and joy.
My brilliant mentor Michael C. Corballis guided me through my master’s degree, my PhD, and several subsequent collaborations. He is an academic gentleman, intellectual treasure, and exemplary scientist I cannot thank enough. From the early days of this project I would also like to mention the support of my late parents, Heinz and Hanni Suddendorf, as well as of Barbara Gerding, Pam Oliver, Richard Aukett, Shayne Carter, Owen Sweetman, Paula Nightingale, Matt Donaldson, Tina Forster, and Dave Rickard. I am grateful to many others with whom I discussed my ideas in New Zealand, Germany, and Australia. Thanks to Angela Dean and Darryl Eyles for the title suggestion “Mind the Gap” and for giving me Richard Holmes’s exquisite book The Age of Wonder. The books that have inspired me, such as Jared Diamond’s Guns, Germs, and Steel and Tim Flannery’s The Future Eaters, cannot all be listed here. Instead I want to thank all those authors who contributed to the works listed in the full version of the references. It is only through having access to what oozed out of their minds that I could construct this view of the gap.
My first attempt at turning this project into a popular science book began in 2003 at the University of Queensland, and I would like to thank the support of my colleagues Ottmar Lipp, John McClean, Mark Nielsen, Virginia Slaughter, and Valerie Stone. Special thanks goes to Valerie for her contributions to the 2004 attempt to start telling this story. Thanks to my many students in the courses Learning and Cognition, Evolutionary Approaches to Human Behavior, and Evolutionary and Comparative Perspectives on Cognition who, over the years, have helped me clarify my thoughts and develop my passion for teaching. I have had the pleasure of working with many excellent postgraduate students at honors, master’s, and PhD level, and I would like to especially note the contributions of my doctoral students Janie Busby, David Butler, Emma Collier-Baker, Jo Davis, Janine Oostenbroek, and Jonathan Redshaw.
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