Read The Making of the Mind: The Neuroscience of Human Nature Online
Authors: Ronald T. Kellogg
The Making of the Mind: The Neuroscience of Human Nature
Published 2013 by Prometheus Books
The Making of the Mind: The Neuroscience of Human Nature.
Copyright © 2013 by Ronald T. Kellogg. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, digital, electronic, mechanical, photocopying, recording, or otherwise, or conveyed via the Internet or a website without prior written permission of the publisher, except in the case of brief quotations embodied in critical articles and reviews.
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Cover image © 2013 Media Bakery
Cover design by Grace M. Conti-Zilsberger
The Library of Congress has cataloged the printed edition as follows:
Kellogg, Ronald Thomas.
The making of the mind : the neuroscience of human nature / by Ronald T. Kellogg.
pages cm
Includes bibliographical references and index.
ISBN 978-1-61614-733-4 (pbk.)
ISBN 978-1-61614-734-1 (ebook)
1. Cognitive neuroscience. 2. Neuropsychology. I. Title.
QP360.5.K45 2013
612.8'233—dc23
2013010071
Printed in the United States of America
The origin of the human mind is as lost as a grain of sand in the Sahara. It is impossible to say precisely when the psychological ingredients of modern human minds made their entry into the world because minds do not leave fossils that can be dated and interpreted by scientists. Today, we can examine the living organ of the mind—the human brain—as it perceives, thinks, remembers, and imagines by means of the recently invented tools of neuroimaging. Ancestral brains, on the other hand, turned to dust long ago, whether their owners once lived thousands, tens of thousands, or hundreds of thousands of years in the past. All that remain now are portions of the skull that once housed a human mind, or the bones of the legs that enabled upright walking, or the hands that enabled the crafting of tools or visual artistry. Although no one knows for certain when the modern human mind first appeared, archeologists point to abundant evidence of its activity dating from forty thousand to ten thousand years ago in the Upper Paleolithic or Late Stone Age. By then, the mind within us was at work in the world creating ancient art of unmistakably human origin.
In the south of France, not far from Cahors, in the Midi-Pyrénées region, is a cave called Pech Merle. My visit there in the summer of 2005 was prompted by the chance to see prehistoric cave paintings created by early modern humans. At first appearances, the cave at Pech Merle was indistinguishable from those limestone caves carved by water in the valley of the Mississippi River back home in St. Louis. The crucial difference appeared only deep in the cave, far from the entrance, when the tour guide shined his flashlight on a wall adorned with hauntingly beautiful images of human hands and spotted horses.
These and many other images in the cave were created by human beings in the Upper Paleolithic era of prehistory. Using carbon 14 dating, archeologists estimate the age of the spotted horse at about 24,640 years old.
1
Because of the location of the painting in Pech Merle, it can be inferred that the artist or artists had specific memory abilities well known in contemporary cognitive neuroscience. The artist responsible for the spotted horses had to retrieve an image of a horse from long-term memory and maintain it in a temporary store referred to as working memory. By comparing a visual-spatial representation in working memory with the image unfolding on the cave wall, the artist would have been able to create an accurate representation. Because the work was done deep in the cave, the model for the drawing was not present in visual sight. Indeed, the artist had to work from some kind of torch light to even see the creation underway. Conceivably, the artist might have been recollecting a specific horse seen at some point in the past, using a capacity for mental travel back in time, or it may have been a more general memory of the concept rather than a specific instance. Alternatively, perhaps the artist was simply imagining a horse that could have differed from any specific horse ever before encountered. Cognitive anthropologists have in fact wondered whether the images were a product of the hallucinogenic imagery of a shaman. Although it had been thought by biologists that wild, predomestic horses had only coats of black or bay, the spotted pattern found in the images of Pech Merle in fact were painted from memory rather than fantasy. The genes responsible for the spotted-leopard pattern found in some modern horses were also identified in DNA samples of horse remains in Western Europe dated to the Pleistocene, the geological epoch ending ten thousand years ago, just prior to the Holocene epoch of today. The same pattern was not found in Asian samples from the Pleistocene, suggesting that all horse colors observed in Paleolithic art in fact were found in the prehistoric horse populations where the caves were located.
2
The artwork of the Upper Paleolithic provides vivid evidence of a modern human mind. It indicates that modern humans were living in Europe by forty thousand years ago, although they likely originated earlier in Africa, as will be discussed later in the chapter. The makers of the cave paintings and carved figurines were fellow members of
Homo sapiens
just like us today. Archeologists
have discovered thousands of pieces of Paleolithic art rendered on limestone cave walls as well as small objects of stone, bone, antler, and ivory that are associated with the fossils of human remains. Although such artwork has been found in several parts of the world, the most intensively investigated and well-known collection comes from southwestern Europe. In the cave at Lascaux in southern France alone, for example, more than fifteen hundred images adorn the walls.
3
Animals are a frequent subject matter, but images of humans, and anthropomorphic-type images that combine parts of an animal (e.g., antlers) with a human figure, are also common. Abstractions in the form of geometric signs are also observable. Unmistakably, the creators of these works were capable of using visual symbols to represent ideas.
During the Upper Paleolithic, there is clear evidence of an explosion of cultural creativity. Besides the cave paintings and sculptures, archeologists document an increased sophistication in tool making and weaponry, and a wide variety of body adornments. This explosion of Upper Paleolithic culture has been referred to as a “human revolution” or the “dawn of human culture” or “a great leap forward” as a way of highlighting the discontinuity with the artifacts produced by earlier members of the hominid lineage.
4
For example, neither
Homo neanderthalis
nor
Homo erectus
left artifacts comparable in their sophistication, variety, and sheer number as those created by
Homo sapiens
. Scholars disagree as to whether the change to the modern mind was as sudden as implied by the concept of “a great leap forward” or instead reflected a gradual accumulation of changes starting back even further in the past.
5
In either case, by forty thousand years ago humanity had crossed the Rubicon, setting the mind within us apart from all other creatures. How is the human mind so fundamentally distinctive? The aim of this book is to provide a novel answer to this question by drawing on contemporary research in cognitive social neuroscience.
By analyzing what has been learned in recent decades about the neuroscience of our cognitive and social abilities, it is possible to identify the most important distinctive features of the mind within us. Major advances have been made with the invention of tools, such as functional magnetic resonance imaging (fMRI), that allow one to infer neural activity as cognitive functions take place in the living brain. Importantly, the brain of a twenty-first-century
human being has the same structures and distinctive cognitive capacities as the brain of the Upper Paleolithic artist. It was this brain—the one we can investigate today with the tools of contemporary neuroscience—that enabled us to invent culture and exploit cultural change over relatively brief periods of historical time. The capacity for logical inference exhibited by the scientists who analyzed the DNA of horses to draw conclusions about the cave paintings of the Upper Paleolithic was already present in the prehistoric originators of the art. In like manner, the capacity for planning that enabled humans in the twentieth century to land on the moon was already manifest in our prehistoric ancestors. As the noted paleontologist Stephen Jay Gould observed, “Cultural change has brought most of us through hunting and gathering, past the explosive new world triggered by agriculture, and into the age of atomic weaponry, air transportation and the electronic revolution.” This cultural change was brought about with “the same brain that enabled some of us to paint the caves of Chauvet and the ceiling of the Sistine Chapel.”
6
Evolutionary theorists explain the constancy of the human brain over the past forty thousand years in one of two ways. The classical Darwinian view of gradual change over vast periods of geological time holds that tens of thousands of years is insufficient time for significant biological change to occur. A different view, and the one favored by Gould, is that species typically remain static in form over tens of thousands of years with no gradual change at all. When a new species emerges through natural selection, speciation takes place relatively rapidly—as a saltation rather than a slow gradual accumulation of differences. The abrupt transition associated with the formation of a new species is then followed by a new equilibrium where no change at all is observable for long periods of time. This alternative to Darwinian gradualism is called the punctuated equilibrium model of evolution.
7
In any event, the essential point for the thesis of this book is that we can understand the causes of the “human revolution” during the Upper Paleolithic by investigating the brain and mental capabilities of modern human beings alive today. With the recent advances in the cognitive sciences fueled in part by the invention of technology for imaging the living brain, it is now possible to outline why the mind within us is so distinctive.
The premise of stasis in the fundamental distinctive features of the human
does not conflict with the fact that some simple adaptations have occurred over the past ten thousand years. For example, with the invention of agriculture and the domestication of cattle in the final Neolithic phase of the Stone Age (8000–9000 BCE), a dietary adaptation occurred to allow the consumption of milk during adulthood. The hunter-gatherers of prehistory needed the lactase enzyme required to digest milk early in life while nursing, but then it was turned off during maturation. A mutation in the gene responsible for turning off the production of lactase allowed even adults to consume milk, an adaptation that eventually spread widely among Europeans.
8
The kind of adaptations that resulted in the modern human brain—something akin to adding wings with which to fly—were far too complex to occur rapidly in thousands of years. An example is the human capacity to innovate and plan new ways of living, as was required for the invention of agriculture in the first place.
THE ENSEMBLE HYPOTHESIS
One straightforward and common answer to the mystery of “human revolution” is that the brain expanded or reorganized symbolic thought. Symbols are certainly evident in the cave paintings in the form of representational art. A visual symbolic representation is used to refer to a horse, a bull, a deer, a bison, or another human being. A capacity for symbolic thought could have facilitated the ability to think about abstract concepts that are not tied directly to perceptual experience. Closely related to this hypothesis is that the brain expanded or reorganized to support language, where words are used as symbolic representations, and the use of visual-spatial symbols. If either of these hypotheses is correct, then there should be evidence from neuroscience of an obvious change in the brain from nonhuman to human species. Or, coming at the question from the level of the genes responsible for the development of the brain, there ought to be a mutation in a gene or set of genes that accounts for the distinctive feature of human brain maturation related to symbol use or language.
The thesis of the present book adopts a related but more complex point of view. The argument here is that there was not a single major addition to or reorganization of the brain and cognitive functioning in the advent of modern
human beings. Instead, the findings of cognitive social neuroscience document the addition of five parts that together comprise the modern mental ensemble. Each part reflected a reorganization of the brain of our immediate hominid ancestors—in some cases this reorganization could have been relatively minor, such as an advance in the executive functioning of working memory; in other cases, the reorganization probably was more significant, such as in the step to using abstract symbols in thought rather than concrete perceptual representations. The central point is that changes occurred on multiple fronts, from small to moderate. Looking at each part in isolation, it might have been possible to discern with ease the continuity with (and specific nature of) the change from our immediate ancestor, had the evidence not long ago turned to dust. But small to modest changes took place on several fronts. This certainly meant that a greatly expanded brain needed to accommodate the sum of the changes. Besides a change in brain quantity, a profoundly important change in quality also occurred because each part interacted with one or more other parts. The parts must be considered together, with each understood only in relation to the whole. The ensemble hypothesis contends that the interaction of the parts, not just the increase in brain size, yielded the dramatically different mind within a modern human.
Here human symbolic thought and language are viewed as so closely interwoven as to constitute just one of the five key parts. Contemporary research in the neurosciences has extensively documented four others that are crucial for the ensemble. One is an advanced working memory, particularly the executive functions that enable planning and self-regulation. Another is an advanced social intelligence that enables humans to collaborate, empathize, and transmit culture from one generation to the next through imitation and other means of social learning. The next part involves a modification of language for the purpose of silent thought rather than vocal communication. As language became interiorized as inner speech, it combined with a capacity to make causal inferences. This part is called
the interpreter
because it explains the contents of our conscious experiences. Lastly, long-term memory in humans underwent a specialization in the ability to recollect specific episodes from our past experience. This episodic form of long-term memory allows one to recall what, when, and where a specific event occurred. Further, it allows one to
imagine an event occurring in the future using the same mental capacity. For this reason, the fifth and final part of the ensemble is referred to as
mental time travel
. The modern human mind can roam into the past of our autobiographical experience or venture forward in the imaginary future with equal ease.