In the beginning was the ape. As I’ve mentioned, around six and a half million years ago our ancestors were similar to chimpanzees. They had brains roughly the same size as chimpanzee’s brains, and probably had roughly similar mental abilities. It is reasonable to think that the social behavior of this ancestral ape was similar to that of chimpanzees—i.e., that they lived in fission-fusion communities, were territorial, xenophobic, and didn’t hesitate to kill their neighbors.
For the next four million years, evolution of the human lineage proceeded slowly. Then, about two million years ago, a new primate species called Homo erectus stepped out on the African savannah.* Erectus looked much more human than any of its predecessors, but what was most remarkable about the new creature was its brain, which doubled in volume over the next million years. Homo erectus got smart—much smarter than any primate species that came before. They created large stone tools (the beautifully crafted Acheulean “handaxes”) and built campfires. They probably hunted cooperatively and consequently consumed more meat than their predecessors. They may even have invented cooking.27 Homo heidelbergensis (“Heidelberg Man”) evolved from Homo erectus approximately 600,000 years ago, and Homo sapiens evolved from Homo heidelbergensis roughly 200,000 years ago. Soon after, anatomically modern humans—Homo sapiens sapiens—came into being. These people were almost exactly like you and me physically, but they were very different mentally, in ways that I’m going to clarify in just a moment.
The forces that transformed anatomically modern humans into psychologically modern humans were mainly cultural. Human culture was born in two great spasms. The first began about forty thousand years ago in what’s known as the Upper Paleolithic revolution. As prehistoric humans transitioned into this period, stone tools made a huge leap in sophistication. They became more specialized and incorporated new materials such as bone and antler. For the first time, people hafted stone points to wood to make spears and harpoons, and used spear-throwers to increase their force and distance. Soon works of art appeared—beautiful paintings on cave walls across southern Europe, and small stone and ivory sculptures. Then, eight to ten thousand years ago, the Neolithic revolution exploded in the Middle East (and somewhat later elsewhere) as human societies underwent a cascading sequence of transformations. People abandoned an economy based on hunting and gathering, and turned to agriculture and animal husbandry. They domesticated wild plants and animals, and anchored themselves in permanent settlements. Agriculture led naturally to the ownership of land, and to technologies for cultivation, irrigation, and storing surplus grain. As settlements expanded into towns and cities, increased population density made way for social stratification, divisions of labor, and increased trade. The new towns and cities required administrative structures, which were interwoven with religious institutions.
During their journey through time, prehistoric humans acquired a range of mental aptitudes that we take for granted today, but which were almost certainly absent during the earliest stages of hominid evolution. These include the psychological traits that are necessary conditions for dehumanization, namely:
1. A domain-specific folk-biology module responsible for parsing the biological world into natural kinds (species) and making inferences about them.
2. A domain-specific folk-sociology module responsible for parsing the social world into natural kinds (ethnoraces) and making inferences about them.
3. A domain-general capacity for second-order thought that makes it possible to reflect on one’s own mental states.
4. An intuitive theory of essences used to explain why there are natural kinds.
5. An intuitive theory of natural hierarchy (great chain of being) for ordering the natural world.
It’s reasonable to think that our common ancestor with the chimpanzee didn’t have any of these (or at best had only the first of them), and we know that present-day humans have all of them. So, all five psychological traits must have emerged over the last six and a half million years or so. Determining when all five of these pieces were in place should allow us to set a lower limit for when dehumanization began. Of course, this sort of reasoning won’t tell us exactly when people started dehumanizing each other, because although the five conditions that I listed above are individually necessary, they may not be (in fact, they probably aren’t) jointly sufficient.
Because the evidence is indirect and often sketchy, it’s difficult to draw conclusions about prehistoric people’s psychology. But it’s possible to make some educated guesses, and that’s what I’m going to do right now.
We can begin with the folk-biology module, which is probably the most ancient of the five. It’s very helpful for an animal to be able to distinguish what it eats from what eats it, and any animal that does this has to have at least a rudimentary ability for responding differentially to different biological kinds. But as we saw in the example of ant “warfare,” an animal can behave differently in relation to different species without having concepts of biological kinds or being able to make inferences about them. The predator-detecting abilities of fancier animals—for example, vervet monkeys—are closer to what we’re looking for. Vervet monkeys distinguish between leopards, pythons, and eagles, and give distinctive alarm calls for each, but it’s not clear that they have concepts of these animals.28 Chimpanzees probably have primitive concepts of biological kinds, and our common ancestor may have had them as well. However, we can be certain that a well-developed folk biology was in place by the time our prehistoric ancestors had become accomplished hunters. People who depend on hunting for a significant portion of their diet need to have detailed knowledge of the animals that they hunt (this is also true, to a more limited extent, of the intellectual demands of gathering). They need to have a refined understanding of the way that a variety of animals behave under a range of circumstances, They need to have expert tracking skills, including the ability to identify hoof-and pawprints, various kinds of feces, and other marks that animals leave on their environments, and when they migrate into new territories, they have to be able to quickly learn about the behavior of newly encountered species—in part, by making similarity-based inferences.
Archaeological evidence suggests that meat was a significant component of Homo erectus’s diet, although opinion is divided about whether this came primarily from hunting or from scavenging the carcasses of animals brought down by large predators. Whatever the facts are about Homo erectus, we know that prehistoric Homo sapiens excelled at cooperative hunting. We also know that they dispersed out of Africa to exploit a wide range of habitats where they encountered, and learned to hunt, many unfamiliar species. None of this would be possible unless they were competent to make inferences about animal behavior. So a well-developed module for intuitive folk-biology is likely to have been in place by the middle Paleolithic period, perhaps 100,000 years ago.29
The next puzzle concerns our knack for second-order thought. Many cognitive scientists believe that second-order thought is tightly bound up with language. The idea is that being able to use and understand language makes it possible for a person to reflect on their own mental states. Philosopher and cognitive scientist Andy Clark explains how this works:
Rather amazingly, we are animals who can think about any aspect of our own thinking and can thus devise cognitive strategies … aimed to modify, alter, or control aspects of our own psychology.… [A]s soon as we formulate a thought in words … it becomes an object both for ourselves and for others. As an object, it is the kind of thing that we can have thoughts about. In creating the object, we need have no thoughts about thoughts, but once it is there, the opportunity immediately exists to attend to it as an object in its own right. The process of linguistic formulation thus creates the stable structure to which subsequent thinkings attach.30
These don’t have to be words that come out of one’s mouth. They can be words that one silently “says” in one’s head. The point is that once a person expresses a thought as a sentence, in whatever medium, then he or
she can think about that sentence. So, once prehistoric people were able to do this, they were in a position to think about their own thoughts. What a remarkable achievement this was! Tufts University philosopher Daniel Dennett hypothesizes that higher-order thought emerged in two steps. Early on, hominid brains had various domain-specific cognitive systems. These special-purpose mental organs weren’t integrated with one another—there wasn’t any information flow between them. But even though these cognitive systems operated autonomously, they were adequate for negotiating the practical challenges that these primates had to face—challenges like obtaining food, avoiding predators, finding mates, and so on. Then language evolved. Linguistic communication was a tremendous boon to those who could use it. Valuable information could rapidly move from mouth to ear, and thereby hop from brain to brain, with high fidelity. This vastly accelerated the speed of cultural transmission.
Without language to help it along, the spread of ideas is painfully slow. You can get a sense of just how slow from observations of cultural transmission among nonhuman primates. One of the most impressive examples concerns a community of Japanese macaques living on the island of Koshima. In 1953, scientists studying these monkeys began provisioning them with pieces of sweet potato. The potatoes were placed on the beach, so to avoid getting their mouths full of grit, the macaques had to get rid of the sand clinging to the food before eating it, which they accomplished as best they could by brushing off the sand with their hands. Then one day a young female named Imo (Japanese for “yam”) discovered that she could rinse the potatoes in river water, which noticeably produced a superior result. Before long other macaques (first her siblings, and then her mother) began to wash their potatoes, too, and the practice eventually spread to the entire troop. Today, over fifty years later, descendents of the original group continue to wash their potatoes (nowadays in salt water, perhaps as a method of seasoning).31 But even among clever Japanese macaques it took nearly a decade for potato washing to become a cultural fixture.
Language turbocharged the spread of culture, but communicating ideas wasn’t the only thing that language was good for. It was also good for thinking with. Language reconfigured the way that human brains process information by bringing second-order cognition into being. Here’s Dennett’s story of how this happened:
Then one fine day (in this rational reconstruction), one of these hominids “mistakenly” asked for help when there was no helpful audience within earshot—except itself! When it heard its own request, the stimulation provoked just the sort of other-helping utterance production that the request from another would have caused. And to the creature’s delight, it found that it had just provoked itself into answering the question.32
Of course, Dennett doesn’t want us to take his charming fable literally. His point is that once language became established, people could use it to elicit information from themselves that they weren’t aware that they had. Language did more than enable people to talk to other people; it also permitted parts of brains to “talk” to one another through the medium of linguistic thought. Once this happened, the mind became what Dennett calls a Joycean machine: a site of ongoing inner dialogue pulling together information from far-flung regions of the brain.
This is a good story, but is there any evidence that things actually happened this way?
Because evidence about the psychology of long-dead people is always meager, it’s easy to dismiss any attempt to reconstruct the evolution of the human mind as the wildest of speculation. But this would be too hasty. Our knowledge of the remote past comes primarily from the evidence uncovered by archaeologists. Nowadays, archaeology has a subdiscipline called cognitive archaeology that uses material evidence from the prehistoric past to generate and test hypotheses about our early ancestors’ minds. Steven Mithen, a cognitive archaeologist at the University of Reading in the United Kingdom, argues that the archaeological evidence supports a scenario very much like the one described by Dennett. Mithen argues that our early ancestors evolved a suite of cognitive modules that equipped them for dealing with the practical exigencies of life. Then, around 200,000 years ago Homo sapiens evolved, and so did language. It took another 50,000 years or so for language to develop and proliferate enough to become a regular feature of human life. Once established, the use of language made it possible to integrate information from separate cognitive domains, and achieve what Mithen calls cognitive fluidity. This creative crisscrossing of cognitive domains heralded the explosion of culture during the Upper Paleolithic period. From that point onward, culture had an overwhelmingly powerful impact on the development of our species.33
If Dennett and Mithen are correct, the evolution of language had three important consequences: it facilitated communication and therefore the spread of culture, it unified the mind by integrating domain-specific modules, and it made second-order thinking possible. Now, here’s an interesting question. What did the original second-order thinkers think about? What reflections preoccupied them the most? This question isn’t quite as baffling as it might seem, because these women and men left a record of their thoughts in their works of art. The magnificent murals that adorn the walls and ceilings of caves across southern Europe are festooned with realistic portraits of animals: horses, deer, cattle, bison, lions, birds, bears, goats, mammoth, and wooly rhinoceros. There’s practically nothing else in these pictures—no trees, clouds, mountains, rivers, campfires, or shelters—and the same is true of their sculptures and engravings.
Although painting a picture or carving a sculpture is, in many ways, different from putting a thought into words, the two forms of expression have something important in common. When you put a thought into words, or an idea into a picture, you’ve externalized it. You’ve turned your thought into a representation: a thing that you can think about. But unlike spoken language, which is transient, art leaves a record. So, by looking at people’s art, we can get insights into what sorts of things they reflected on.
Paleolithic art shows that these men and women were deeply—one might even say, obsessively—preoccupied with thoughts about biological kinds. They were reflecting on their thoughts about animals, and asking questions about those thoughts. Prior to this point, prehistoric people had biological concepts—for example, the concept porcupine—but now, for the first time, they could wonder about what it is that makes something a porcupine. It seems reasonable to think that they came to the same intuitive conclusion that people do today. They concluded that what makes an animal an animal of a certain kind is its essence. Porcupines are porcupines because they have the porcupine essence. The members of every species have something inside of them that makes them members of that species.
There are also representations of human beings in Paleolithic art. The human presence in art shows that men and women of the Upper Paleolithic weren’t just thinking about horses and bison. They were also thinking about themselves. Following the same pattern of explanation, we can suppose that, when Paleolithic people asked themselves, “What makes us human?” the answer that they gave was, “Having a human essence.”
Let’s suppose that this is what happened. Conceiving of human beings as having a shared essence must have radically transformed their pattern of social interaction. Let me use an example to illustrate why. Imagine that you encounter a virulently racist man—a man who hates and despises black people and advocates laws that discriminate against them. If you wanted to persuade this man to adopt a more enlightened attitude, how would you go about it? I think that you’d likely appeal to a common humanity. You would call his attention to the fact that black people are human beings, just like he is. From a strictly logical point of view this doesn’t make much sense. Why should a reminder of shared species membership have any impact on a person’s attitudes? I think that the best way to make sense of this is as follows: Thinking of a person as a member of the same species as yourself, as sharing the same essence, automatically evokes a sense of oneness with them. You perceive them as a fellow member o
f the human community. By conceiving of a person in this way, you conceive of them as a member of your in-group, and this triggers inhibitions against harming them.
If I’m right, this implies that when Upper Paleolithic people began thinking of themselves as sharing an essence, this must have counteracted their xenophobic tendencies. It must have made them more willing to interact with people outside of the limiting boundaries of their communities. There’s evidence that this occurred: The first unequivocal evidence of trade comes from this period, and trade can only happen if communities are open to friendly contact with one another.
Seashells from the Mediterranean appear at Upper Paleolithic sites several hundred kilometers north in central Europe; fossilized amber from the Black Sea is found in central Russia (up to 700 km away).… But the most compelling examples are associated with the production of tools from certain types of stones that were routinely transported 100–200 km (and up to 400 km for more distinctive high-quality flint) from Upper Paleolithic quarry sites in north central and eastern Europe … and … it is safe to assume that trade in purely local goods and services (e.g., perishable foodstuff, housing, and, especially, labor services) had already reached a considerable level of intensity.34
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