In this groundbreaking look at the evolution of our brains, eminent neuroscientists Gary Lynch and Richard Granger uncover the mysteries of the outsize intelligence of our ancestors, who had bigger brains than humans living today. Weaving together history, science, and the latest theories of artificial intelligence, Lynch and Granger demystify the complexities of our brains, and show us how our memory, cognition, and intelligence actually function, as well as what mechanisms in the brain can potentially be enhanced, improving on the current design. Author of The Emotional Brain, Joseph LeDoux praised it as "provocative and fascinating," and, writing in the New Scientist, Willian Calvin called it "a popular account of how brains enlarge, in both evolutionary and developmental terms" and "a much needed book."
About the Author
Gary Lynch is one of the most cited neuroscientists in the world and author of more than 550 scientific articles. He is Professor of Psychiatry at the University of California at Irvine. Richard Granger is the WH Neukom Distinguished Professor of Computational Sciences at Dartmouth. He is internationally recognized for his work in experimental neuroscience.
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The Origins and Future of Human Intelligence
By Gary Lynch, Richard Granger
Palgrave MacmillanCopyright © 2008 Gary Lynch and Richard Granger
All rights reserved.
BIG BRAINS, BIGGER BRAINS
Somewhere in Africa, sometime between five and six million years ago, began a process that led to an unprecedented outcome: the domination of the planet by a single species.
A typical mammal—a lion, a horse—has a world population of thousands to hundreds of thousands; but humans are now numbered in the billions. Typical mammals have locales, niches, in which they live: polar bears in ice, wolves in forests, apes in jungles. But we humans have broken out of our habitats and have fashioned almost the entire world into extended homes for ourselves. Animals kill other animals, for food and competition; but we humans manage to wipe out entire species, and kill ourselves by the thousands at a stroke.
And other animals communicate and even learn from each other, conveying apparent "cultural" knowledge. But no animal other than the human has any way to pass complex information to their great-great-grandchildren, nor can any other species learn from long-dead ancestors. Humans can do so, via language.
These differences all originate in one place. Species differ from each other in terms of bones, digestive systems, sensory organs, or other biological machinery; and until recently, these differences determined the winners and losers in the endless competition among life forms. But the human difference is as clear as it is enigmatic: it is our minds, and the brains that create those minds, that let us dwarf the abilities of other animals.
How did we get these brains, and how do they confer these unmatched capabilities?
These questions draw from many fields of study. Biology examines organs, from kidneys to pancreas; but brains are organs that uniquely produce not just biological but mental phenomena. Neuroscience studies brains; but brains are encoded and built by genetics, evolution, and development. Psychology studies the mind; but our minds are composed of our brains, their environments, our ability to learn, and our cultural surroundings. The countless facts and data compiled from scientific studies can overwhelm our understanding; but computational science synthesizes disparate facts, building them into coherent testable hypotheses; identifying candidate operating principles that may underlie the machinery of our brains.
This book marshals these disparate realms of scientific knowledge to ask how, a few million years ago, our ancient forebears began to grow brains far beyond their normal size; how the functions of those brains changed; and how that process led to who we are now.
The answers not only address what our brains can do, but what they cannot do. Humans build vast systems of roads, and vehicles, and power plants, but we struggle with their planning and their unexpected outcomes. We make scientific discoveries about our world, mastering mechanics, electricity, medicine; but it's not easy, and decades may go by between advances. Human societies develop complex economic and political organizations, but we barely understand them and often cannot control them. An understanding of how we arrived as the dominant creature on earth includes understanding our limits, the constraints on our mental powers ... and glimpses of how we may overcome those constraints.
The path that led from ancient humans to ourselves is sometimes viewed as a relatively straight line of progress, from primitive to modern. We will show that it has been a path full of false starts and dead ends; of apparently aimless wandering interrupted by surprising leaps. Along the way, we will illustrate some of the remarkable turning points that led here, and introduce some of the ancient hominids who arose, and passed away, before we humans arrived.
Perhaps the most remarkable occurrence in our evolutionary history was the rise and fall of one of our very recent relatives. We'll introduce them, and use their similarities and differences as touchstones in our examination of ourselves. From the first discovery of their fossil skeletons and skulls, to reconstruction of their extraordinary brains, and inferences about their minds and their culture, their exceptional story will inform our own. For a time, they shared the earth with us; they walked the plains of southern Africa barely 10,000 to 30,000 years ago. They had most of our traits; they looked a lot like we do; and they were about our size ... but their brains were far larger than our own.
Dr. Frederick W. FitzSimons had just been appointed the director of the Port Elizabeth Museum in 1906, and he took his new duties seriously. The little museum, which was tucked upstairs from the wool and produce markets in this small port town at the tip of South Africa, was in severe disrepair. "No real attempt at systematic classification, arrangement, or adequate labeling had hitherto been attempted," FitzSimons reported. "No efficient means had been taken to protect the specimens from the ravages of destructive insect pests."
FitzSimons closed the museum and had it thoroughly cleansed and refurbished. "I am pleased to state," he reported in 1907, that "I have completed the reidentification, classification, labeling, numbering and cataloguing," and that "further ridicule and criticism in regard to the state the Museum is in at present will be silenced." Upon its reopening, FitzSimons instituted a broad outreach program called "Popular Nights," offering public exhibitions, and featuring live snake shows. Local residents flocked to the performances, and the museum's reputation grew.
So Port Elizabeth Museum was naturally the place that came to mind in the autumn of 1913, when two farmers from the small inland town of Boskop dug up pieces of an odd-looking fossil skull on their land.
FitzSimons was as careful with these new bones as he had been with his museum. He quickly recognized that the specimens indeed formed a skull that was human, or strongly human-like; but he also realized what was most strange: the skull was simply too large. Neanderthal fossils had been found, with slightly bigger braincases, but this new one was huge. FitzSimons immediately saw that this was a stunning find: physical evidence of a human with a far bigger brain than our own. He performed a set of convincing measurements, and fired off a letter to the flagship science journal of the British Empire, Nature, describing the skull, noting its unique volume, and speculating about the heightened intelligence that would have come with its increased brain size. The skull's name, and the name of the heretofore unknown peoples that it represented, derived simply from the region in which it was found: these people were the Boskops.
The find was just as shocking to others as it had been to FitzSimons, and it didn't take long for the top anatomists and anthropologists of the world to get involved. Their subsequent examinations confirmed, and even extended, FitzSimons' initial estimate of the Boskop brain. Most estimates put the cranial capacity at 25 percent to 35 percent bigger than ours. Further digs were carried out in ensuing years, and more skulls, of equally superhuman size, were discovered. Neanderthal skulls, which had been discovered decades earlier, had large brain capacities but were shaped differently, with prominent bony ape-like brow ridges and less forehead than our own. But these new skulls had huge size along with fully human features. A human-like fossil in the Skhul caves in Qafzeh, Israel, had a brain capacity of roughly 1650 cubic centimeters, 20 percent larger than ours. Fossil skulls found at Wadjak in Indonesia, and at Fish Hoek in South Africa, each have 1600 cc capacities. Dozens of skulls from Europe, Asia, and Africa exhibit similar huge size, including familiar skulls that were found in the caves of Cro-Magnon, in southwestern France. (See table in Appendix). Boskops are the largest of them all, with estimated brain sizes of 1800 to 1900 ccs—more than 30 percent larger than ours. These brain cases have rising foreheads like our own, and have been found accompanied by slim, clearly human-like skeletons. The Boskops were around our size, between five and six feet tall. They walked upright. They had light, slender bones, and small, trim bodies—topped by very big brains.
Multiple scholarly articles were written about the Boskops and their brethren, and it became widely appreciated that a stunning discovery really had been made: previous humans had been bigger-brained, and likely smarter, than modern-day humans. Sir Arthur Keith, the most prominent anatomist in the British Empire, and president of the Royal Anthropological Institute, declared that Boskop "outrivals in brain volume any people of Europe, ancient or modern."
These discoveries caused a sensation in the early twentieth century. They were the subjects of conferences, the lead stories in newspapers, and were widely discussed in the scientific community. They raised a raft of questions: What does it mean to have a bigger brain? Are big brains definitely better? If so, how did their possessors die out while we Homo sapiens survived? Did they have brains that differed from ours, or did Boskops have the same abilities as we do? In particular, could they talk? Were they actually smarter? And ... if they were such a big deal, why have most of us never heard of them?
ARE BIGGER BRAINS BETTER?
A human brain averages roughly 1350 cubic centimeters in volume, with normal brains easily ranging from 1100 to 1500 cc. From human to human, bigger isn't necessarily better: some very intelligent and accomplished people have small brains, and vice versa. At two extremes, satirist Jonathan Swift had an apparently giant brain of roughly 1900 cc, while equally noted writer Anatole France reportedly had a brain that barely topped 1000 cc. Geniuses are no exception. Einstein's brain reportedly measured an average and undistinguished 1230 cc.
For different members of the same species, a bigger brain may well be unimportant. But between different species, brain size can mean a lot.
Brains, like any other body part, are partly scaled to the overall body size of the animal. Bigger animals tend to have bigger brains, just as they have bigger eyes, feet, and bones. But some animals have features that don't seem to fit their overall body size: the neck of a giraffe, the teeth of a tiger, the trunk of an elephant. So if we measure the ratio of a body part to the overall body, most will maintain the normal size relations, while some will stand out from that scale.
On that scale, humans have normally-sized eyes, bones, and feet. But compared to other animals of our size, we have excessively huge brains. Our brains are smaller than an elephant's, but human brains are disproportionate: for our body size they are much larger than those of any other creature. Our nearest relatives are chimpanzees; if you take a chimp and a human of roughly equal body size, the person's brain, at roughly 1,350 ccs, will outweigh the chimp's brain by more than three times. For the same body mass, we have the equivalent of more than three of their brains.
This is unprecedented; if you chart the relation between brain size and body size, as we will in chapter 11, most animals will stay very close to the predicted ratios; humans will be wildly distant from them. One could argue that our brains are our defining feature, setting us apart from all other creatures in the world.
Indeed, it's our great brains, and our resulting intelligence, that changed everything in the world. Our vast population, our colonization of every corner of the earth, our remolding of physical features of the planet; all are new phenomena in a mere ten thousand years, after billions of years of life before humans.
What is it in our brains that led to our dominance, and what is it in Boskops' bigger brains that didn't?
BRAIN AND LANGUAGE
We can list the feats of intellect that differentiate us from all other animals: we make a dizzying array of tools, from saws and wrenches to wheels and engines; we heat cold places and cool down hot ones; we cook food; we travel huge distances around the globe; we build houses, roads, and bridges. These reflect many different abilities, but all are related by a hidden variable: our language ability. Ask yourself who it was, for instance, who discovered fire, or invented the saw, or the boat, or roads, or shoes. The reason it is very hard to answer these questions is that they were invented over time, by multiple individuals, who took what came before and improved upon it. The key here is that these unknown humans built on what came before.
Other animals interact with each other, and even learn from each other. There is evidence of other primates passing along "cultural" information and skills. But no animal other than us can pass on arbitrary information at will and across generations.
Dogs, whales, chimps, apes, don't have this advantage. Each is born to roughly the same world as their ancestors, and to make an invention they would have to do so themselves, within their lifetime. We have the unique ability to tell others something: something in addition to, beyond elemental, necessary skills. We can be told by our parents what a house is, what clothes are, what pencil and paper are; and in time we can tell our children, who can tell their children. Our individual brains take their jumping-off point from a mass of accumulated information that gets passed to us through language. Some chimps may have two parents, and a few teachers; language can give us the equivalent of thousands of teachers.
As an individual, a person may see a primitive boat and think of improvements to it—but as a group, we can pass that boat design on to many, and ensure that no individual will ever again have to re-invent it before improving it.
The process can fail. Indeed, such gaps have occurred in information transmission even within our short history of human culture. In the Renaissance, people saw the great domes of the Pantheon and other ancient buildings, which had been built a full thousand years before, and realized that they no longer possessed the ability to build such structures. The knowledge had been lost during the Middle Ages, after the fall of the Roman Empire and the concomitant loss of masses of written information and instructions. The Renaissance artists and engineers had to rediscover what the Romans had already known generations ago.
Language preserves knowledge outside of brains, and passes it from one brain to another. Whatever communicative abilities other animals have, our human languages have powerful characteristics that other animals don't possess. If we inherited our brains from our primate precursors, did they have some form of language? If they did, what did their language abilities look like?
And did the Boskops' bigger brains give them even greater powers of language? Or were their brains somehow deficient, bypassing the route to language? If they had it, why did they fail where we succeeded? If they didn't have it, why not, and what is it about our brains that gave us this ability?
WERE BOSKOPS SMARTER?
Brains are amazingly similar across all primates, from chimps to humans. Even the brains of dogs, and mice, and elephants, are all far, far more similar than they are different. We're all mammals, and the basic design of our brains was firmly laid down in the earliest mammalian ancestors, when they diverged from the reptiles more than 100 million years ago. The design has barely deviated since then, from the parts in a brain, and the patterns of their connections to each other, all the way down to the individual neurons that comprise them, and the detailed biochemistry of their operation.
But if the brains of a mouse, a monkey, a mammoth, and a human all contain the same brain designs, what are the differences? Chimps are smarter than most animals, aren't they? Elephants have great memories, don't they? Dogs' sense of smell can sniff out minute clues better than other animals, can't they? We will show that these differences are actually extremely minor variations of the same underlying abilities. Chimps are smart because their brains are relatively large, not because those brains are different. Most mammals have the same great memories as elephants, whether or not we carefully test it. Dogs' keen sense of smell is shared by most mammals (though not us primates); we use dogs for tracking because we can train them.
And our own brains have most of these same designs and abilities. The primary difference, overwhelming all others, is size; compared to those of all other animals, our brains are many times too large for our bodies. With the great expansion of our brains came vast new territory to store immense tracts of memory, whose sheer extent changed the way we behave. Can it really be that changing the size alone can change its nature; that pure quantity can improve quality?
We'll show the small differences and vast similarities between ourselves and our primate relatives, and we will raise the question of size thresholds that may have to be passed for certain abilities to show up. Bring water to 99 degrees celsius, and it's hot water; raise it just one degree more, and it has new qualities. We will show what human brain changes look like, and explain the principles that enable them to occur. In general, larger mammalian brains show new abilities, as a dog outperforms a mouse, a chimp over a sloth, a human over an ape.
Excerpted from Big Brain by Gary Lynch, Richard Granger. Copyright © 2008 Gary Lynch and Richard Granger. Excerpted by permission of Palgrave Macmillan.
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Table of Contents
Contents1 Big Brains, Bigger Brains,
2 The Mind in the Machine,
3 Genes Build Brains,
4 Brains Arrive,
5 The Brains of Mammals,
6 From Olfaction to Cognition,
7 The Thinking Brain,
8 The Tools of Thought,
9 From Brain Differences to Individual Differences,
10 What's in a Species?,
11 The Origins of Big Brains,
12 Giant Brains,
13 All but Human,
14 More than Human,