Evolving Brains, Emerging Gods
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FIGURE 3.1 Archaic Homo sapiens: an empathetic self.
Although the temporo-parietal junction appears to be critical for reading other people’s minds, it functions as part of a network with frontal lobe structures. Neuroimaging studies of individuals thinking about other people also report activities of the anterior cingulate, insula, and medial prefrontal cortex. The anterior cingulate and insula are critical brain areas for thinking about the self, as described in the last chapter, so it is not surprising that they are also important in thinking about others. The overlapping functions of these two brain areas have been noted by many researchers. The anterior cingulate has been said to be “one of several critical areas in tasks related to ‘theory of mind.’ ” And the insula has been said to play “a fundamental role” in the mechanism by which “we understand what others feel.” For example, in a study in which subjects watched videos of other people apparently experiencing injuries, both the anterior cingulate and insula were activated.24
Additional frontal lobe structures are also involved in the theory of mind brain network. This includes the frontal pole (BA 10), discussed in chapter 1 as being critical for perception, information processing, social cognition, the processing of emotions, and other functions. It is noteworthy that the skull of Homo floresiensis, the dimunitive hominin found in Indonesia and thought by many researchers to be another species of Archaic homo sapiens, also had an enlarged frontal polar region, suggesting that it may also have developed a theory of mind. Another prefrontal area connected to the theory of mind network is the frontal cortex (BA 8).25
There is one other neuroanatomical aspect of the theory of mind that is of interest. In 1996 it was reported that monkeys have neurons in their brains that fire whenever the monkey performs a goal-directed action but also fire whenever the monkey observes a similar action in another monkey. These neurons have been called mirror neurons. Neuroimaging studies have suggested that humans also possess a diffuse network of mirror neurons, widely spread in the cortex, including the insula and inferior parietal areas. Since these neurons are affected by the behavior of others, it has been speculated that “this mirror neuron mechanism may be part of, or be a precursor to a more general mind-reading ability.” For example, it has been proposed that “it is thanks to mirror neurons … that we flinch at the sight of someone else hit suddenly by a fist or a ball and wince while reading a gruesome account of torture.” Although the mirror neurons present an intriguing model for possibly understanding the neurological basis for a theory of mind, it is premature to draw any conclusions, especially since monkeys possess these neurons but have never been shown to have any awareness of others’ thoughts.26
THEORY OF MIND AND BELIEF IN GODS
It has been recognized by several researchers that the acquisition of a theory of mind is a necessary precondition for a belief in gods. For example, in The Belief Instinct, Jesse Bering, a psychologist at Queen’s University in Belfast, detailed how a theory of mind leads to assumptions about gods. He noted that it is only after we acquire a theory of mind that we can imagine the mind of a god. We assume, of course, that the god also has a theory of mind and thus the god can imagine what we mortals are thinking. As Bering summarized it: “God was born of theory of mind.” The requirement that hominins must have acquired a theory of mind in order to believe in a god is also stressed in recent books by University of British Columbia psychologist Ara Norenzayan (Big Gods) and Oxford University biologist Dominic Johnson (God Is Watching You), briefly summarized in chapter 8.27
Creating gods and attributing to them a theory of mind lead to several possible benefits. Most important, it leads to the belief that the gods can read our minds and know what we are thinking. In studies of many religions, the gods are “envisioned as possessing a deep knowing of people as unique individuals—of their ‘hearts and souls.’ ” According to Bering, this led “our ancestors to feel and behave as though their actions were being observed, tallied, judged by a supernatural audience”—in short, to greater social order. Another benefit of creating gods with a theory of mind is that such gods are useful for explaining the unknown features of life, such as lightning being the gods showing anger, and disease being a retribution from the gods.28
Will Gervais, a psychologist at the University of Kentucky, developed a similar thesis regarding the importance of a theory of mind. He asserted that “the same abilities that allow people to represent and reason about each other’s minds may also allow people to represent and reason about supernatural minds.… Therefore, mind perception is absolutely basic to religious cognition.… Mind perception may be the cognitive basis for belief in gods.” Since this is true, reasoned Gervais, individuals who have difficulty understanding other people’s minds should also hold less strong beliefs about gods. As noted earlier, individuals with autism have been said to have some impairment in their theory of mind—“mindblindness.” Gervais cited studies that have reported “a modest but reliable inverse association between the autistic spectrum and belief in God.” In one such study, adolescents with autism, compared to controls, were only 11 percent as likely “to strongly endorse belief in God.” Such findings support the association between theory of mind and theistic beliefs.29
Since theory of mind is related to thinking about gods, Gervais also reasoned that there should be some overlap in the brain regions activated by both thought processes. This has been tested in a series of experiments by Dimitrios Kapogiannis and colleagues at the National Institutes of Health in Bethesda, Maryland. They did neuroimaging on subjects “with varying degrees of self-reported religiosity” to assess the brain areas activated when subjects responded to questions about God’s level of involvement, God’s level of anger, and religious doctrine. There was a modest overlap on the first and third questions with brain areas activated by theory of mind experiments, and the authors concluded that “religious belief engages well-known brain networks performing abstract semantic processing, imagery, and intent-related and emotional ToM [theory of mind].”30
It is very unlikely, however, that Neandertal hominins believed in gods. Although they apparently had acquired a theory of mind, they had not yet acquired a second-order theory of mind that would allow them to think about what god was thinking about them. Nor had they acquired an ability to fully project themselves into the past and future and to use their past experiences to plan the future. In short, they were not yet cognitively mature enough to create and honor the gods. We will return to this question in the following chapters.
Thus, by about 200,000 years ago, Neandertal hominins had brains bigger than those of modern Homo sapiens. They were intelligent and apparently had acquired both an awareness of self and an awareness of others. The combination of these abilities would have provided Neandertals with a significant evolutionary advantage in food acquisition, warfare, trading, and reproduction, since they would have had an ability to think about and predict others’ actions.
However, they apparently still lacked an introspective ability to think about their own thoughts as well as an ability to use the detailed past and present to plan the future.
By 100,000 years ago, hominins had been separated from their primate ancestors for approximately 5.9 million years, 99 percent of the duration from the time of separation to the present. What were the odds, in the remaining 100,000 years, that hominins would build monuments such as Angkor Wat and Chartres Cathedral to honor gods, write Macbeth and Messiah, and fly to the moon? Something remarkable was about to happen.
4
EARLY HOMO SAPIENS
An Introspective Self
Since you have seen the dust, see the Wind; since you have seen the foam, see the Ocean.… Come, see it, for insight is the only thing in you that avails: the rest of you is a piece of fat and flesh.
—Rūmī (1207–1273), “The Grief of the Dead,” Mathnawī, book 4
One hundred thousand years ago, multiple species of Archaic Homo sapiens lived in small groups throughout Africa
, Southeast Asia, the Middle East, and Europe. Australia and the Americas were apparently still devoid of hominins. In appearance, except for having prominent brow ridges, they looked surprisingly modern. If properly dressed and carrying briefcases, they would not evoke undue attention today riding a subway in New York or London.
In behavior, however, they were remarkably primitive and lived pretty much as their ancestors had lived for over a million years. They controlled fire, made tools and weapons, hunted large animals, migrated long distances, and had at least rudimentary methods of vocal communication. At least one species of Archaic Homo sapiens—the Neandertals—had the brain capacity of modern humans, and in fact had had it for 100,000 years, yet they had relatively little to show for it. All Archaic Homo sapiens were probably self-aware and able to recognize themselves in a pool of still water, since they had evolved from Homo erectus. And the Neandertals had also apparently developed a theory of mind, the ability to think about what others were thinking; other species of Archaic Homo sapiens may have done so as well.
However, none of these hominins was apparently yet able to think about themselves thinking about themselves or to fully place themselves in time past and time future with what would be called an autobiographical memory. They would be completely perplexed by modern human interactions, and if you had asked them about their gods, they would probably not have had the vaguest idea what you were talking about.
THE FIRST SPARKS
The earliest definitive archeological evidence for unique behaviors we associate with modern humans comes from individuals who lived in caves and rock shelters in the Middle East and on the southern tip of Africa beginning about 100,000 years ago. The hominins in the Middle East had apparently migrated from Africa and were living in the same region where Neandertals were living at that time, and genetic studies suggest that the two groups interacted. Since there is no evidence that these African travelers survived over time or spread further, it is assumed they eventually died out or returned to Africa. However, they left behind some pierced shell beads and red ochre pigment that have been dated to 100,000 to 115,000 years ago; these may be the first known examples of self-decoration.1
The evidence from the caves in South Africa is more definitive and is dated to between 75,000 and 100,000 years ago. It includes highly sophisticated stone tools and weapons, produced by heating the cutting edge in a fire and then pressure flaking it to make the tip “thinner, narrower and sharper.” Some of the stones chosen for use came from sites 20 miles or more distant from where the tools and weapons were being made. Cambridge University archeologist Paul Mellars claims that these stone tools and weapons from South Africa were as good as those made at European sites 50,000 years later. Also impressive was the finding of “28 shaped and polished bone tools,” the first appearance of bone being used as a tool or weapon, since the bone tools used by the Neandertals appeared later. Bone tools have also been found in the Congo and dated to at least 75,000 years ago. There is also “circumstantial evidence” in South Africa for the use of snares for trapping small animals and bows and arrows for hunting, the first such appearance in history. By 65,000 years ago, the use of bow and arrow technology is more definitive.2
The people who lived in the South African caves and rock shelters ate a varied diet that included seafood and local game. They also lived a reasonably settled existence, using bedding made from various grasses and plants, including some plants that have “chemicals that have insecticidal and larvicidal properties against, for example, mosquitos.” Such plants may also have been used by these people as herb medicines.3
Of great interest was the finding in these caves of seashells, dated to 77,0000 years ago, that were covered with red ochre and appear to have been deliberately perforated, thus allowing them to be strung together as a necklace or bracelet. The use of red ochre to decorate necklaces or bracelets in South Africa is consistent with the prominent role ochre played in that culture. A 100,000-year-old “ochre-processing workshop” was recently uncovered in these same caves. As noted in the previous chapter, ochre can be used for tanning skins, as an insect repellent when applied to the skin, and for hafting stone tools onto wood handles, as well as for body decoration. Thus, it is not possible to say definitely what the ochre was being used for 100,000 years ago, but the fact that it was applied to the perforated shells suggests that it was, at least occasionally, being used for decoration. In addition to the perforated shells found in the Middle East and South Africa, others dated to 75,000 years ago or earlier have been found in Morocco and Algeria, suggesting that self-decoration was widespread. Altogether, five different kinds of shells have been identified. Among the South African shell beads, it was found that “beads from two separate [archeological] layers displayed patterns of wear distinct from one another, which suggested that they had been strung and worn differently at different times.” This may be the first evidence of an evolving hominin fashion statement.4
Also of interest in the South African caves was the finding of 15 pieces of ochre that had been modified by scraping and grinding, then deliberately engraved with a sharp instrument. The engravings consist of straight lines forming various designs. On one, for example, “the cross hatching consists of two sets of six and eight lines partly intercepted by a longer line.” Some of the engraved pieces of ochre have been dated to approximately 99,000 years ago. Speculation regarding the meaning of the engraved designs has ranged from being some kind of record, to a calendar, to a piece of art. Elsewhere in southern Africa, in what is now Botswana, “a six-meter- long rock was shaped to enhance its resemblance to the head of a snake” and was dated to 70,000 years ago. Such findings led the authors of the South Africa findings to suggest that, “at least in South Africa, Homo sapiens was behaviorally modern” by this time.5
There is also evidence that the inhabitants of the South African caves had begun to wear fitted clothing at this time. Hominins had presumably been using animal skins for warmth for thousands of years, especially those members of Homo erectus and Archaic Homo sapiens who lived in colder climates in Europe and Asia. However, there are suggestions that about 72,000 years ago modern humans began to wear more fitted clothing, even in hotter climates, and that the clothing was more tailored than simple animal skin capes. The clothing presumably consisted of fitted animal skins, since any evidence of woven cloth or bone needles did not appear for an additional 40,000 years. The evidence for the introduction of fitted clothing consists of genetic studies of human lice and the fact that the body louse diverged from the head louse about 72,000 years ago. Body lice have claws adapted to clinging to clothing, not skin, and only lay their eggs in clothing. According to researchers involved in these studies, the “ecological differentiation [of body lice] probably arose when humans adopted frequent use of clothing.”6
In addition to these behaviors, groups of hominins who lived in Africa at about this time also began to travel widely. These were, of course, not the first hominins to leave Africa; Homo erectus had left more than a million years earlier, and its descendants were widely distributed from Europe to Indonesia. But the migration of early Homo sapiens out of Africa would be different. As science writer Carl Zimmer summarized it: “In an evolutionary flash, every major continent except for Antarctica was home to Homo sapiens. What had once been a minor subspecies of chimp, an exile from the forests, had taken over the world.”7
In addition to the early Homo sapiens who went to the Middle East about 100,000 years ago, there may have been other early Homo sapiens who left Africa. The major exodus, which led to the worldwide distribution of modern Homo sapiens, is thought to have occurred about 60,000 years ago, although, as noted previously, recent modifications of the dating of such events have suggested that this exodus may have occurred much earlier. If the exodus was 60,000 years ago, it is not clear why they left at that time. The eruption of the Toba supervolcano in Indonesia 73,000 years ago, which is thought to have affected the world climate for hundreds of years, may ha
ve been a factor. The number of Homo sapiens who left Africa at that time has been variously estimated at from 1,000 to a few thousand. They probably left by crossing from what is now Ethiopia to Yemen at the mouth of the Red Sea, which, because sea levels were much lower at the time, was only a few miles wide. It is widely thought that there were also subsequent migrations, but their numbers and timing are not yet clear.8
It is possible to re-create the worldwide peregrinations of early Homo sapiens by mapping the genetic variations of the male Y chromosome and female mitochrondrial DNA in present-day Homo sapiens. One group followed the coastline through what is now Oman, Iran, Pakistan, and India and continued down the Malay Peninsula through Myanmar (Burma), Thailand, and Malaysia to Indonesia, which was then connected by land. Evidence for their presumed shoreline migration is underwater, since sea levels are now much higher than at that time. In following this route, early Homo sapiens encountered groups of Archaic Homo sapiens who had descended from Homo erectus. It is now clear that Homo sapiens interbred with these groups, since some Southeast Asians today carry small amounts of Neandertal DNA, while others carry DNA from the Denisovans, as noted previously.9
Early Homo sapiens reached Indonesia by at least 50,000 years ago. If they had moved at a pace of only two miles per year, the entire 8,000-mile journey from Africa would have taken about 4,000 years. Unlike Homo erectus, however, early Homo sapiens did not end their journey in Indonesia. Instead, they built boats, probably by tying together logs and reeds, and crossed approximately 40 miles of open ocean to reach Australia, which was connected to Papua New Guinea and Tasmania at that time. Although hominins had used makeshift boats to cross rivers and narrow stretches of water for thousands of years, this was apparently the first time a more extended water crossing had been made and was indicative of the planning skills of early Homo sapiens. The water crossing apparently involved a significant number of people; computer simulations based on the genetics of present-day Australians “suggest that more than just a boatload or two of colonists founded the area’s present aboriginal population.” There is evidence for Homo sapiens settlement in Australia 50,000 years ago, in Papua New Guinea between 49,000 and 43,000 years ago, and on the Melanesian island of New Ireland more than 30,000 years ago.10