The Evolutionary Road to Human Memory PDF
Preview The Evolutionary Road to Human Memory
The Evolutionary Road to Human Memory The Evolutionary Road to Human Memory ELISABETH A. MURRAY STEVEN P. WISE MARY K. L. BALDWIN KIM S. GRAHAM 1 3 Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Oxford University Press 2020 Excerpt from JURASSIC PARK: A NOVEL by Michael Crichton, copyright © 1990 by Michael Crichton. Used by permission of Alfred A. Knopf, an imprint of the Knopf Doubleday Publishing Group, a division of Penguin Random House LLC. All rights reserved. Excerpt from THE HITCHHIKER’S GUIDE TO THE GALAXY by Douglas Adams, copyright © 1989 by Pan Macmillan. Reproduced with permission of Pan Macmillan through PLSclear. 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Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2019947387 ISBN 978– 0– 19– 882805– 1 Printed and bound by CPI Group (UK) Ltd, Croydon, CR0 4YY Oxford University Press makes no representation, express or implied, that the drug dosages in this book are correct. Readers must therefore always check the product information and clinical procedures with the most up-t o- date published product information and data sheets provided by the manufacturers and the most recent codes of conduct and safety regulations. The authors and the publishers do not accept responsibility or legal liability for any errors in the text or for the misuse or misapplication of material in this work. Except where otherwise stated, drug dosages and recommendations are for the non-p regnant adult who is not breast-f eeding Links to third party websites are provided by Oxford in good faith and for information only. Oxford disclaims any responsibility for the materials contained in any third party website referenced in this work. To every child who ever loved a stegosaurus. Preface Apes and astronauts In the novel Planet of the Apes,1 a chimpanzee named Zira “ape-s plains” evolution to a human astronaut. Marooned on the planet Soros, the astronaut prompts Zira by asking whether apes evolved from humans on her planet. “Some of us thought so,” she begins, “but it is not exactly that.” Apes and men are two separate branches that have evolved from a point in common but in different directions, the [apes] gradually developing to the stage of rational thought, the [humans] stagnating in their animal state. Many orangutans, however, still insist on denying this obvious fact. To most of us, the astronaut’s question seems topsy-t urvy. How could apes have evolved from humans? Apes lack language and live in the open; humans talk cease- lessly and complain bitterly if their roof leaks— even a little. On the planet Soros, it’s the other way around. Humans can’t speak, and they live in the wild. Orangutans govern society; chimpanzees assist them (with more than a little resentment); and gorillas enforce the law. Orangutans also dominate the scientific establishment despite the fact that “a line of great thinkers, all of them chimpanzees” made all the big breakthroughs. When the astronaut crash- lands on Soros, an injury renders him mute for a while, but that doesn’t stop him from having something to say about the apes’ view of humans as lower, “sub-a pe” primates. Once his voice recovers, he intends to har- angue an orangutan about this offensive attitude, but first he listens to Zira explain why her planet has garrulous gorillas and dumb humans. The “ape’s brain,” she claims, has become more “developed, . . . complex, and organized, whereas man’s has hardly undergone any transformation.” The ape’s mind was primarily the result of the fact that he had four agile hands . . . With only two hands, each with short, clumsy fingers . . . man is probably handi- capped at birth, incapable of progressing . . . viii Preface Clearly, Soros awaits the evolution of gender-n eutral language. But despite her old- fashioned word choices, Zira gets a few things right. On Earth, at least, humans and apes did “evolve from a point in common.” But in her oration on origins, Zira gets a lot wrong. She claims that the human brain “stagnated” on Soros while the ape brain underwent Earth- shattering changes. As the novel unfolds, readers learn that Zira— a chauvinistic chimp— underestimates human intelligence. More importantly, her statement exposes a serious misconception about evolution. After two species split from their “point in common,” both usually change. Although there are exceptions to this rule (called living fossils), neither humans nor apes were likely to have “stagnated” during evo- lution on Soros, and nothing of the sort happened on Earth either. Zira also expresses frustration about getting her ideas accepted. “Many orangutans,” she complains, “still insist on denying” obvious facts. Entrenched sci- entific doctrines are difficult to dislodge on planet Earth, too, and the result is the same as on Soros: enduring scientific error. In this book, as in our tome on the same topic,2 we challenge a widely accepted theory about human memory. That view— the one you’ll find on the internet, in textbooks, and in just about every brief summary of the subject—i s simple and popular but fundamentally wrong. It as- signs human memory to a small corner of the brain called the “medial temporal lobe.” This one brain area is said to be responsible for all of the memories that shape the human mind. So, what’s our beef with this idea? To begin with, the medial temporal lobe makes up about 2% of the brain, and it seems strange that such a tiny bit of brain would underlie all human memory. What’s the rest of the brain doing? This question is simple, but our answer is not. We believe that as a series of now-e xtinct ancestors adapted to life in their world, millions of years ago, new brain areas appeared, each of which supported an innovative form of memory that we’ve inherited in modi- fied form. Taken together, these areas make up most of the brain: closer to 80% of it than to 2%. Memory, at least as we see it, reflects a journey along a long evolu- tionary road, which left its legacy in the human brain. Animals and attitudes In Chapters 9 and 10, we’ll discuss some ways in which human memories differ from those in other animals. It’s a hard sell, in part because claims of human ex- ceptionalism have a checkered past. Scarcely a week goes by without a news article proclaiming that some species has a cognitive capacity previously thought to be uniquely human. Indeed, so many prior claims have ended up on the scrapheap that one scientist, Frans de Waal, has called for a moratorium on claims of human uniqueness. Similarities between human and parrot vocalizations are said to dis- credit the stodgy doctrine that only people can talk; claims about ape “language” preface ix attract endless publicity; and many animals are said to have the same tool use, rea- soning, and emotional experiences as people do. These articles imply that animals and humans have the same cognitive capabilities, but narrow- minded, pig-h eaded scientists like us refuse to accept this enlightened attitude. Despite objections to human exceptionalism, many scientists continue to rec- ognize a substantial cognitive divide between humans and animals.3– 6 Slowly, the idea that each species has its own distinctive set of cognitive capacities is gaining ground. We mean no offense to other species when we say that their cognitive lives differ from ours. Three of the authors have spent their entire careers studying animal brains and behavior. Collectively, and in no particular order, we’ve studied rats, cats, and bats; bears and bushbabies; tree shrews and turtles; squirrels, opos- sums, chickens, voles, mice, and ferrets; along with six species of monkeys. We admire these and other animals for what they are: not exactly like us, but not com- pletely different either. That statement isn’t an opinion; it’s a fact, one that results from another, equally well- established fact: humans and every animal species alive today have an equally long evolutionary history, much of it common but recently separate. Both parts of our evolutionary history—t he common part and the sep- arate part— have left their mark on human memory. Areas avoided We neglect several topics that you might expect to find in a book on memory. Birds, for instance, have astonishing memories,7 often surpassing anything we can do. Songbirds establish exquisite memories of their songs, which they never forget; people are known to bungle the lines of their national anthem. Scrub jays have precise memories about where and when they stashed food; some of us have trouble remembering where we’ve put our keys. But we don’t have any birds, or anything like a bird, among our ancestors. Although we share many extinct an- cestors with birds, our last common ancestor neither sang like modern songbirds nor cached food like jays do today. We are vertebrates, mammals, primates, and anthropoids, among other things; but we are not birds, so we don’t discuss them much in this book. We also avoid ethics, religion, and philosophy. Although we mention conscious- ness from time to time, we ignore its neural basis for the most part. We don’t deal with creationism or the pseudoscience called “intelligent design.” And, because we know that animal research is necessary for a deep understanding of the brain and its disorders, we rely heavily on this crucial branch of science and ignore any con- troversies about it. Finally, we say almost nothing about how the brain establishes memories, how the brain develops and matures, how to improve memory, or how to deal with memory disorders such as Alzheimer’s disease. Nor do we provide a comprehensive x Preface description of human memory. These are all important topics, but not for the story that we want to tell. And the gist of that story is this: as a series of our direct an- cestors faced the problems and opportunities of their time and place, their brains developed new forms of memory that helped them gain an advantage in life. Sometime during human evolution, yet another new kind of memory emerged. It ignited the human imagination, established ownership of knowledge, and em- powered every individual, day upon day, to add new pages to the story of a life. References 1. Boulle, P. Planet of the Apes (New York, NY: Ballentine, 1963). 2. Murray, E. A., Wise, S. P., & Graham, K. S. The Evolution of Memory Systems: Ancestors, Anatomy, and Adaptations (Oxford, UK: Oxford University Press, 2017). 3. Penn, D. C., Holyoak, K. J., & Povinelli, D. J. Darwin’s mistake: explaining the discon- tinuity between human and nonhuman minds. Behavioral and Brain Sciences 31, 109– 130 (2008). 4. Passingham, R. E. What Is Special about the Human Brain? (Oxford, UK: Oxford University Press, 2008). 5. Suddendorf, T. The Gap: The Science of What Separates Us from Other Animals (New York, NY: Basic Books, 2013). 6. LeDoux, J. E. & Pine, D. S. Using neuroscience to help understand fear and anxiety: a two- system framework. American Journal of Psychiatry 173, 1083– 1093 (2016). 7. Emery, N. J. Bird Brains: An Exploration of Avian Intelligence (Princeton, NJ: Princeton University Press, 2016). Acknowledgments We thank Brad Postle and Georg Striedter for helpful comments on a draft version of this book, along with Peter Rudebeck and Carly Jones for comments on selected chapters. Samantha White and Hannah Goldbach gave us invaluable feedback over the summer of 2017, and we thank Mark Laubach for arranging those discussions. We are also grateful to our editors at Oxford University Press, Martin Baum and Charlotte Holloway, who provided support throughout this project.
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