THE HUMAN REVOLUTION REVISITED
The evolution of autobiographical memory, allowing modern Homo sapiens to more skillfully utilize the past to plan the future, could largely explain the human revolution that began approximately 40,000 years ago. Tools and weapons would have been rapidly improved as humans incorporated their experiences from the past in planning for their needs in the future. The widespread use of memory devices at this time reflects an increased interest in keeping records for past events, such as the number of reindeer killed last fall, and predicting future events, such as the next full moon.
In view of the development of autobiographical memory, how should we interpret the outpouring of visual art at this time? In interpreting the art, however, it is important to keep in mind that our theorizing is based solely on the art that has survived and been discovered. As Paleolithic art expert Jean Clottes noted, “It is certain that we know but a fraction of the caves which were painted and/or engraved.”60
The main theme of the art of this period, as noted, is animals, especially those being hunted. Such animals were central to the survival of these people; for example, wild horses and reindeer were “the foundation of the humans’ diet.” Thus, the most parsimonious explanation is that the artists were depicting things they had seen in the past or hoped to see in the future. Such an explanation is supported by the fact that “15 percent of these animal paintings depict animals that have been wounded by spears or arrows,” thus suggesting they are hunting scenes. Such paintings may also have been used to teach children about animals and how to hunt, and children’s footprints have been found in several of the caves.61
What about the handprints in the caves? Perhaps they are the equivalent of Paleolithic graffiti, the universal way of saying, “I was here.” Such graffiti are a record of where the person was in the past as well as a message for future observers. That would be consistent with the newfound ability of modern Homo sapiens to project themselves into the future. Niaux Cave in southwestern France has paintings dated to about 13,000 years ago, but it also has graffiti left by visitors to the cave in recent centuries, including an individual named “Ruben de la Vialle,” who left his name in the cave in 1660. Is this really different in intent from the much earlier handprints?62
It is also possible that some of the art reflects the newly developing religious ideas, especially the belief in spirits. Given the abundance of animals, some of the art may represent the spirits of animals. A belief in animal spirits is widespread in the world. In some cultures, it is believed that the animal is the ancestor of humans; such an animal is called a totem and is found most strikingly among Australian Aborigines and Northwest Coast Indians. Adherents of a totemic interpretation of the painted caves point to the predominance of specific animals in specific caves and to the half-human, half-animal figures. They also point to a collection of bear skulls in Chauvet Cave, one of which was prominently placed on a rock. As one scholar summarized the scene: “Somehow, some way, this room was a shrine to cave bears, which were honored in unknowable rituals.”63
If animal or other spirits were present in the painted caves, they may have also been used to explain the unknown. Providing explanations for events that are not understood is a function of almost every religious system that has been described. Thus, the animal spirits may have been invoked to explain why the reindeer were late that year in arriving at the river crossing, or why a young man suddenly became sick the day after a bear crossed the trail in front of him.
More elaborate religious explanations of the painted caves have also been proposed. French prehistorian Jean Clottes is regarded as a world authority on prehistoric art, and in 1998 Clottes and South African archeologist David Lewis-Williams published The Shamans of Prehistory. Then, in 2003 Canadian archeologist Brian Hayden published Shamans, Sorcerers, and Saints, expanding on this theme. Shaman was originally a precise term denoting the indigenous healers among the Tungusian tribes in Siberia who healed by undergoing a trance state. Subsequently, it has been used much more broadly to refer to seers who can foretell the future or control the weather, sorcerers who can cast spells, and priest-like individuals who act as intermediaries between this world and the afterworld. The use of shaman in discussions of the painted caves appears to focus mostly on their priest-like function.64
The shamanistic interpretation of cave art postulates that priest-like shamans existed at the time when the caves were painted and that much of the cave art was a product of their trance states. The caves themselves are said to be passages to the underworld of the dead so that people who walked through the caves “were completely surrounded by the underworld.” The handprints on the cave walls are interpreted as attempts by people to contact the underworld. The geometric figures are said to represent visual hallucinations seen by the shamans while in a trance. Specific parts of the cave are said to have been designated for various spiritual functions, including a meeting place for secret societies. The half-human, half-animal figures are said to represent the shamans. Abbé Henri Breuil, a French Catholic priest who spent his life studying cave art, originally designated the most famous one as the “sorcerer of Trois Frères” but later called it the “god of Trois Frères.”65
But were gods present in the painted caves? As discussed in the preface, the term gods has sometimes been used very broadly to include any kind of supernatural beings, including animal spirits. If such a broad definition is used, then probably gods were present in the painted caves. However, if gods is defined more narrowly, as the term is more commonly used, to indicate male or female divine beings who are immortal and who have some special powers over human lives and nature, then it seems less likely that gods were present in the painted caves.
What about religion—was it present in the painted caves? As noted in the preface, the answer to this depends on which of the many definitions of religion you select. Edward Tylor defined religion broadly as “the belief in spirit beings,” thus qualifying as religion any activities in the painted caves that involved spirits, animal or otherwise. Similarly, using the broad definition proposed by French sociologist Émile Durkheim, the worship of totems would qualify as a religion, since, according to Durkheim, “a religion is a unified system of beliefs and practices relative to sacred things.” In fact, Durkheim regarded the worship of totems as the “simplest and original form” of religion, and he studied and wrote about totem worship among Australian Aborigines. If, on the other hand, a religion is defined more narrowly, as William James suggested, as “the feelings, acts, and experiences of individual men … as they apprehend themselves to stand in relation to whatever they may consider the divine,” with divine said to be “godlike,” then it seems less likely that the spiritual activities in the painted caves would have qualified as a religion.66
Given this broad range of interpretations of the meaning of the cave art, what is likely to be the correct one? In fact, it seems unlikely that there ever was a single correct interpretation. The art covers more than 20,000 years, a period 10 times longer than the period from the birth of Jesus to the present. The creation of the art in any given cave often covered several centuries—Chauvet Cave approximately 8,000 years, Cosquer Cave 6,000 years, and even Lascaux Cave, in which most of the art is similar, up to 1,000 years. Given such time spans, attempts to interpret the precise placement of specific art within a cave, as if it had been arranged all at once by an interior decorator, seem futile.67
At a minimum, the cave art would appear to depict things the artists had seen in the past or hoped to see in the future. The animals, especially those with arrows or spears in them, may be attempts to magically ensure the success of the hunt. Such attempts at “hunting magic” have been described by anthropologists among contemporary groups of hunter-gatherers, and this interpretation of the cave art was popular in the last century.68
It is also possible that the animals depicted were believed to be totems, ancestral spirits of humans. This is especially likely to have been th
e case in the later years of this period. Some of the animals depicted in the last painted caves even overlap in time the animals depicted at Göblecki Tepe beginning approximately 11,500 years ago, by which time the evidence for ancestor worship by humans is stronger, as will be discussed in the next chapter.
However, the evidence for a shamanistic or more elaborate religious activity in the painted caves is questionable. It seems premature to call a half-human, half-animal figure a “god” or to postulate the existence of secret societies, presumably based on shared religious beliefs. Such things are possible, but the existing evidence does not appear to support them. Such excessive religious speculation of cave art has also been criticized by archeologist Dale Guthrie as denigrating to the people of that period: “This magico-religious paradigm … has presented early peoples in a distorted light as superstitious dolts totally preoccupied with mystical concerns. Yet the evidence from Paleolithic art tells a quite different story; it portrays people in close touch with the details of a complex earth. Religious images probably do occur, but they are part of a larger mosaic of experience.”69
In view of the development of autobiographical memory, how should we regard the placement of valuable goods in burials, a practice that was becoming widespread at this time? Goods may be placed in graves for many reasons, as Edward Tylor noted more than a century ago. Such reasons include burying the deceased person’s favorite personal items; burying an item as a sign of affection for the deceased; and burying the deceased person’s personal items so that their spirit will not return to the house looking for them.70
The most common reason for burying personal items in a grave, however, is so that those items will be available for use by the deceased in the afterlife. As Ian Tattersall observed, “Burial of the dead with grave goods … indicates a belief in an afterlife: the goods are there because they will be useful to the deceased in the future.” Similarly, Steven Mithen has argued that “it is difficult to believe that such investment would have been made in burial ritual, as at Sungir, had there been no concept of death as a transition to a non-physical form.” This interpretation of grave goods is also consistent with the practice by some groups of killing people so that they can serve the deceased in the afterlife. In his Primitive Culture, Tylor included many examples of this practice prior to the arrival of missionaries. For example, “the Caribs … sacrificed slaves on a chief’s grave to serve him in the new life, and for the same purpose buried dogs with him, and also weapons.” Grave goods are thus one of the most dramatic examples of the effects of autobiographical memory and its associated belief that humans continue to live in another world after their body dies.71
THE BRAIN OF MODERN HOMO SAPIENS
As modern Homo sapiens was gradually acquiring a fully mature autobiographical memory approximately 40,000 years ago, what was happening to their brain? Newly expanding brain areas were acquiring new functions, older brain areas were being reprogrammed, and the white matter connections between them were being improved. The temporal self and the brain of modern Homo sapiens were evolving together.
Substantial research has been carried out to identify the brain areas that are associated with autobiographical memory. To assess this, individuals are subjected to brain imaging while being asked to focus on specific kinds of memories. A review of 19 such studies identified multiple brain areas that were highly activated, as seen in figure 5.2. Several of the identified areas were identical to areas activated by thinking about others (theory of mind), described in chapter 3. These include the anterior cingulate (BA 24, 32), part of the inferior parietal lobule (BA 39), and the adjacent posterior superior temporal area (BA 22). One study, for example, reported that the “inferior parietal cortex was particularly active during retrieval of self-referential information.”72
FIGURE 5.2 Modern Homo Sapiens: a temporal self.
The prefrontal cortex is also activated by autobiographical memory tasks, especially the frontal pole (BA 10) and orbital frontal cortex (BA 47). Studies of the brains of individuals with frontotemporal dementia, in which almost all autobiographical memory is lost, have reported that the orbital frontal cortex is severely damaged. A study of young adults in which subjects were asked to think about the details of their first day at school, first kiss, and so on reported that the “medial prefrontal cortex (MPFC) was specifically engaged in the retrieval of recent AMs [autobiographical memories].” A review of frontal lobe function similarly reported that “the frontal lobes, in particular the frontal poles, are involved in uniquely human capacities, including self-awareness and mental time travel.” This is also consistent with the fact that individuals who have sustained damage to their prefrontal cortex have impairments in thinking about the future equally as often as they have problems in thinking about the past. As summarized by one research group: “Frontal-lobe-damaged patients respond only to concrete, present situations, having no thought or plans for the future.… Many of the patients described appear to live entirely in the present. Implications of the past and the relation to decisions in the future appear to be significantly hindered.”73
Some of the other brain areas that are activated by autobiographical memory tasks overlap only minimally the areas that are activated by the cognitive tasks previously discussed. Foremost among the other areas associated with autobiographical memory are the hippocampus (which has no BA number) and parahippocampal gyrus (BA 35, 36). Since these are evolutionarily among the oldest brain areas, it is somewhat surprising to find them involved in autobiographical memory, one of the evolutionarily newest human cognitive functions. Since the hippocampus is critical for memory storage, this is an example of an evolutionarily newer brain function co-opting an older brain area for its own purposes. Similarly, the evolutionarily older amygdala is involved in autobiographical memory because such memories are often emotion- laden, and emotion is a function of the amygdala. The hippocampus and amygdala are thus both crucial components of autobiographical memory.74
The importance of the hippocampus, amygdala, and parahippocampal gyrus for the development of autobiographical memory is also suggested by the development of the white matter connecting tracts. The cingulum is a major tract that connects the hippocampus, amygdala, and parahippocampal gyrus to the frontal lobe and parietal lobe structures involved in autobiographical memory. The uncinate fasciculus is also important in connecting many of the autobiographical memory brain areas. It is thus of interest that the cingulum and uncinate fasciculus are regarded as being the two most recently developed white matter connecting tracts in humans, consistent with the recent development of our autobiographical memory.75
Additional brain areas activated by autobiographical memory tasks include the posterior cingulate (BA 23, 31), the adjacent superior parietal area (precuneus, BA 7), and the cerebellum. The posterior cingulate, as noted in chapter 4, plays an important role in introspection. The precuneus, as noted in chapter 1, performs a variety of cognitive, sensory, and visual functions. The finding of the cerebellar involvement in autobiographical memory is somewhat surprising, since it is a very old brain area thought to be primarily associated with motor functions, such as the coordination of movements. However, in modern Homo sapiens the cerebellum has undergone “a rapid expansion … in modern brains” and is now three times larger in modern humans than in chimpanzees of comparable size. A study in which subjects were asked to recall specific past memories produced extensive cerebellar activation, and it was concluded that the cerebellum is part of a network “that initiates and monitors the conscious retrieval of episodic [autobiographical] memory.” The fact that the cerebellum plays such a role is another example of an older brain area being co-opted for a more recently evolved brain function.76 In fact, the more the cerebellum is studied, the more functions it is found to have.
Finally, are there differences between the brain areas activated by autobiographical memories of the past and areas activated by imagining future events? Several studies have addressed this question and
reported remarkably consistent results: the brain areas activated by the two tasks are almost identical. One study noted that “this striking neural overlap is consistent with findings that amnesic patients exhibit deficits in both past and future thinking, and confirms that the episodic [autobiographical memory] system contributes importantly to imaging the future.” They thus concluded that “neuroimaging studies from our laboratory and others reveal striking commonalities in the brain networks that are activated when people remember past episodes and imagine future ones.”77
In summary, by about 40,000 years ago, hominins had completed five important stages of cognitive evolution. As Homo habilis, about two million years ago, they began to become significantly more intelligent, and this trajectory toward becoming progressively smarter continued. As Homo erectus, about 1.8 million years ago, they developed self-awareness. As the Neandertal species of Archaic Homo sapiens, about 200,000 years ago, they acquired an awareness of what others were thinking, called a theory of mind. As early Homo sapiens, about 100,000 years ago, they acquired an introspective ability to think about themselves thinking about themselves. Finally, as modern Homo sapiens, about 40,000 years ago, they developed an autobiographical memory, the ability to project themselves backward and forward in time, using their experiences from the past to plan the future. Each stage in this cognitive evolution was accompanied by anatomical changes in their brain, changes that, at least in broad outline, can now be identified.
Evolving Brains, Emerging Gods Page 14