Evolving Brains, Emerging Gods

Early Humans and the Origins of Religion

E. Fuller Torrey

• Publisher: Columbia University Press
• Year: 2017
• ISBN:
  9780231544863
• Topic: Psychology
• Subtopic: Cognitive Science
• Index: Psychology

Religions and mythologies from around the world teach that God or gods created humans. Atheist, humanist, and materialist critics, meanwhile, have attempted to turn theology on its head, claiming that religion is a human invention. In this book, E. Fuller Torrey draws on cutting-edge neuroscience research to propose a startling answer to the ultimate question. Evolving Brains, Emerging Gods locates the origin of gods within the human brain, arguing that religious belief is a by-product of evolution.

Based on an idea originally proposed by Charles Darwin, Torrey marshals evidence that the emergence of gods was an incidental consequence of several evolutionary factors. Using data ranging from ancient skulls and artifacts to brain imaging, primatology, and child development studies, this book traces how new cognitive abilities gave rise to new behaviors. For instance, autobiographical memory, the ability to project ourselves backward and forward in time, gave Homo sapiens a competitive advantage. However, it also led to comprehension of mortality, spurring belief in an alternative to death. Torrey details the neurobiological sequence that explains why the gods appeared when they did, connecting archaeological findings including clothing, art, farming, and urbanization to cognitive developments. This book does not dismiss belief but rather presents religious belief as an inevitable outcome of brain evolution. Providing clear and accessible explanations of evolutionary neuroscience, Evolving Brains, Emerging Gods will shed new light on the mechanics of our deepest mysteries.

1

THE MAKING OF THE GODS

1

HOMO HABILIS

A Smarter Self

The history of religious belief is rarely given centre stage in grand narratives of the evolution of civilization and of humanity and yet the urge to comprehend the human condition—the quest for soul food—may be just as great as the quest for food and reproductive success.

—Mike Parker Pearson, The Archeology of Death and Burial, 1999

The gods were born following a pregnancy lasting approximately two million years. It took that long for hominin brains to evolve structurally and functionally from being primate-like brains to being brains that possessed the cognitive faculties of modern Homo sapiens. Insofar as an evolutionary origin of deities is correct, the concept of a god would not have occurred to hominins prior to about 40,000 years ago, and the gods themselves would probably not have become fully visible prior to about 10,000 years ago. The human brain, and thus the self-aware human world, would not have been ready for them before that time.

Mammalian brains had, of course, been evolving for 200 million years prior to that time. For the first 140 million years of their existence, mammals were insignificant “small creatures living in the nooks and crannies of a dinosaur’s world.” During those eons, evolution was experimenting with the development of the three-part brain—the forebrain, midbrain, and hindbrain—that forms the central nervous system chassis for all mammals.1

About 65 million years ago, an asteroid apparently struck earth, producing a cataclysm that killed the dinosaurs and many other creatures. Mammals not only survived but thrived in a world now devoid of Jurassic predators. As Stephen Jay Gould noted, “We must assume that consciousness would not have evolved on our planet if a cosmic catastrophe had not claimed the dinosaurs as victims. In an entirely literal sense, we owe our existence, as large and reasoning mammals, to our lucky stars.” Our origin, added Gould, makes Homo sapiens “a kind of cosmic accident, just one bauble on the Christmas tree of evolution.”2

With the disappearance of dinosaurs, mammals rapidly diversified, grew larger, and became the new lords of the earth. The mammalian forebrain increased disproportionately in size compared to the midbrain and hindbrain and eventually occupied most of the space within the skull. As the forebrain grew, it differentiated into the four lobes (frontal, temporal, parietal, and occipital), basal ganglia, hippocampus, amygdala, thalamus, and hypothalamus. Most significantly, the brain developed a thin layer called the neocortex, which has been said to be like a 13-inch pizza covering the four lobes of the brain. According to Georg Striedter’s Principles of Brain Evolution, “The neocortex was the key innovation of mammalian brains,” because it included six layers of neurons, compared to the three layers in the cortex of earlier animals. Since neurons are connected three-dimensionally, both horizontally and vertically, to other neurons, the additional three layers increased neuronal connections exponentially, thereby making possible the processing of much more complex information and thought.3

As part of the diversification of mammals, the first primates appeared approximately 60 million years ago. They proliferated rapidly into hundreds of species, of which 235 species still exist. About 30 million years ago, a group known as New World monkeys (for example, cebus monkeys and marmosets) went their separate evolutionary way, and 25 million years ago the Old World monkeys (for examples, baboons and macaques) did the same thing. The great apes, the group most closely related to us, began dividing about 18 million years ago, with the orangutan, and then the gorilla, starting down separate evolutionary paths. Finally, about six million years ago, the hominins separated from chimpanzees, our closest hominid ancestor.

It is important to note that the hominins did not evolve from chimpanzees as we know them. Rather, both hominins and chimpanzees evolved from a common ancestor that lived about six million years ago. During the intervening time, both the hominin line and the chimpanzee line continued to evolve. Among the chimpanzees, for example, one group became geographically isolated in West Africa about two million years ago, and that group evolved into bonobos, also called pygmy chimpanzees. Insofar as the evolving chimpanzee line was subjected to similar evolutionary pressures as the evolving hominin line was during the 6 million years, it would not be surprising, given the principles of parallel evolution, to find that chimpanzees would develop some cognitive abilities similar to those developed by hominins. Awareness of self, to be discussed in chapter 2, is an example of such parallel development.

THE FIRST HOMININS

The evolution of one species into separate species is usually a gradual process. Thus, Sahelanthropus tchadensis, a fossil found in 2001 in Chad and thought to be at least six million years old, has been classified by some as the first bipedal hominin but by others as a chimpanzee. Its brain capacity was less than 400 cubic centimeters, equal in size to the brain capacity of modern chimpanzees.4

Sahelanthropus tchadensis was followed during the next four million years by Ardipithecus kadabba, Ardipithecus ramidus, and several species classified as Australopithecus—anamensis, afarensis, africanus, garhi, boisei, robustus, aethiopicus, and, from fossils discovered in 2010, sediba. There is much discussion regarding which hominin descended from which other hominin, but in fact there are not yet a sufficient number of specimens to make such determinations with any certainty. The study of early hominin fossils has been said to still be in “the stamp-collecting phase that begins most branches of science.”5

What is clear is that these early hominins had a brain capacity of approximately 400 to 475 cubic centimeters, only slightly larger than that of chimpanzees, and their behavior was quite similar to that of chimpanzees. They spent their days foraging for fruits, nuts, roots, and tubers and retreated to trees to escape predators and to sleep. Some researchers have claimed that some species of Australopithecus used stone tools, but other researchers have been doubtful. The most famous examples of Australopithecus are “Lucy,” whose fossils were found in 1974 in Ethiopia, and three sets of footprints embedded in volcanic ash in Tanzania. We occasionally romanticize Australopithecus and tell ourselves that they were not very different from us, but except for walking upright, they were in fact very different. Because of their rudimentary brain development, they could not think about themselves, they could not boast of their accomplishments, they could not gossip about other australopithecines, they did not worry about what might happen after they died, and they did not worship gods. Thus, it is generally believed that Australopithecus individuals “differed from other African apes (just as the other African apes differed from one another) but they were still apes, in mind if not in body.”6

When Homo habilis evolved approximately two million years ago, the world of early hominins became significantly more interesting, because of both its brain size and its behavior. Homo habilis is generally regarded as being the first hominin to have diverged significantly from its primate ancestors, although its precise relationship to other early members of the Homo species—such as Homo rudolfensis, Homo ergaster, and the recently discovered Homo naldi—is far from settled. Fossils of Homo habilis have been discovered in Ethiopia, in northern Kenya, and especially in the Olduvai Gorge in Tanzania, which Louis and Mary Leakey made famous.

Homo habilis is thought to have lived between 2.3 and 1.4 million years ago, although recent finds in Ethiopia suggest that it may have existed as early as 2.8 million years ago. Its average brain size is estimated to have been about 630 cubic centimeters and thus to have been one-third larger than the brain of Australopithecus.

The larger brain of Homo habilis made it smarter than Australopithecus, and it demonstrated this intelligence by making crude stone tools. This was mostly done by breaking rocks to produce sharp stone edges. Crude stone tools have been found dated to 3.3 million years ago, but those made by Homo habilis were more sophisticated. These have been found in abundance in association with Homo habilis fossils. Although crude, such tools would have been effective for cutting the hides and tendons of dead animals, thus allowing the tool-user to strip meat. The stone tools could also have been used to break open animals’ long bones and extract the marrow, an especially rich source of protein. Animal bones found in association with the stone tools suggest that the tools were used in this way. The bones also suggest that Homo habilis was probably a meat eater, in contrast to earlier hominin species. There is no evidence that Homo habilis hunted animals, so they probably scavenged for animals that had been killed by other animals or had died of old age or disease.

The use of tools is, of course, not unique to hominins. Many birds have been observed using tools, including crows, which use sticks and carefully cut leaves to extract insects from holes, and Egyptian vultures, which drop stones on ostrich eggs to crack them open. Sea otters use stones to break the shell of snails and crabs. Monkeys have been observed using sticks to kill snakes and rocks to crack open oyster shells, and it is well known that chimpanzees use sticks, from which they strip the leaves, to forage in termite mounds, and stones to crack open nuts.

What makes the stone tools used by Homo habilis different is their complexity. According to Cambridge University archeologist Steven Mithen: “To detach the type of flakes one finds in the sites of Olduvai Gorge, one needs to recognize acute angles on the [stone] nodules, to select so-called striking platforms and to employ good hand-eye coordination to strike the nodule in the correct place, in the right direction and with the appropriate amount of force.”7

Attempts have been made to teach chimpanzees and bonobos to make stone tools similar to those made by Homo habilis. One especially clever bonobo, rewarded by food treats, successfully made stone tools, but they were significantly inferior to those of Homo habilis. According to Mithen, the bonobo “never developed the concept of searching for acute angles … or controlling the amount of force in percussion.” Mithen speculated that Homo habilis had already developed cognitive skills superior to those of modern chimpanzees, “an intuitive physics in the mind … perhaps even a technical intelligence.” Such cognitive superiority is supported by evidence that Homo habilis occasionally used one tool to make another tool, such as using a stone flake to sharpen a stick; this behavior is unknown among chimpanzees.8

Additional evidence of the intelligence of Homo habilis includes the fact that they traveled several miles to obtain specific types of stones superior for use as tools. They also carried stone tools to new sites, evidence of planning and anticipation of future use. Archeologist Kenneth Feder of Central Connecticut State University said that such behavior suggests “a high level of planning and intelligence.” Such planning and storage of tools for future use are occasionally found among chimpanzees. An adult male chimpanzee in a Swedish zoo, for example, regularly collected and stored stones prior to the zoo’s opening time, which he then used to throw at spectators across the moat surrounding his enclosure.9

Thus, what was Homo habilis really like? They possessed advanced physical skills and some ability to plan and were clearly smarter than their hominin ancestors. However, despite their greater intelligence, there is no evidence that they possessed self-awareness or any of the other higher cognitive functions that would distinguish later hominins and lead to the emergence of the gods. British psychologist Nicholas Humphrey painted a hypothetical picture of what Homo habilis was like:

Once upon a time there were animals ancestral to man who were not conscious. That is not to say that these animals lacked brains. They were no doubt percipient, intelligent, complexly motivated creatures, whose internal control mechanisms were in many respects the equals of our own. But it is to say that they had no way of looking in upon the mechanism. They had clever brains, but blank minds. Their brains would receive and process information from their sense-organs without their minds being conscious of any accompanying sensation, their brains would be moved by, say, hunger or fear without their minds being conscious of any accompanying emotion, their brains would undertake volunta...