Origin Story, page 17
What Makes Us Different? Crossing Threshold 6
Imagine a team of alien scientists who have been orbiting our planet searching for intelligent life and studying Earth’s life-forms in a longitudinal research project lasting several million years. Two hundred thousand years ago, they wouldn’t have noticed anything unusual about our ancestors. In Africa and parts of Europe and Asia, they might have spotted several species of large, bipedal primates, including the species we call Homo neanderthalensis and Homo heidelbergensis. They might even have seen individuals that a modern human paleontologist would describe as Homo sapiens, because the oldest skull normally assigned to our species is almost two hundred thousand years old. It was found at Omo Valley in Ethiopia in the African rift valley. (In June 2017, human remains from Morocco were dated to three hundred thousand years ago, but their exact relationship to us remains uncertain.) But there was little to distinguish these early humans from many other large or medium-size primate and mammal species. They lived in small, scattered nomadic communities with a total population of, at most, a few hundred thousand individuals. Like all large animals, they gathered or hunted the food and energy they needed from their surroundings.
Today, two or three hundred thousand years later (no time at all for a paleontologist), our orbiting aliens searching for intelligent life would have seen enough changes in the behavior of this particular species to justify a few scholarly high-fives. They would have watched as humans spread around the world. Then, starting from the end of the last ice age, ten thousand years ago, they would have noticed human numbers growing fast. They would also have watched as humans began to change their environments to suit them better by burning down forests, diverting rivers, plowing the land, and building towns and cities. In the past two hundred years, human numbers grew to over seven billion, and our species began to transform the oceans, the land, and the air. Human-built roads, canals, and railways snaked across the continents, linking thousands of human-built cities with populations in the millions. Vast ships navigated the oceans, and planes ferried goods and people through the air and across the continents. Just a hundred years ago, in glowing filaments and patches, Earth started lighting up at night. The aliens’ instruments would also have shown that oceans were getting more acidic, the atmosphere was warming, coral reefs were dying, and polar ice caps were shrinking. Biodiversity was declining so fast that some of the alien biologists might have wondered if this was the start of another mass extinction.
Paleontologically speaking, changes this fast are the equivalent of an explosion. Without planning it, we have become a planet-changing species. We even have the power, if we are foolish enough, to destroy much of the biosphere in just a few hours by launching some of the eighteen hundred nuclear missiles that remain on high alert today. No single species has had such power in the four-billion-year history of the biosphere.
Clearly a new threshold had been crossed. Our alien scientists would surely have been asking themselves, What is it about this strange species?
Historians, anthropologists, philosophers, and scholars in many other fields have wrestled long and hard with the same question. Some feel the question is too complex, too loaded, and too multidimensional to yield a scientific answer. But curiously, when we see human history as part of the larger history of the biosphere and the universe, the distinctive features of our species stand out more clearly. Today, scholars in many different fields seem to be converging on similar answers to the question of what makes us different.
When you see sudden, rapid changes like this, start looking for tiny changes that have huge consequences. Complexity theory and the related field of chaos theory are full of changes like this. Often, they are described as butterfly effects. The metaphor comes from the meteorologist Edward Lorenz, who pointed out that in weather systems, tiny events (the flapping of a butterfly’s wings, perhaps?) can get amplified by positive feedback cycles, generating a cascade of changes that may unleash tornadoes thousands of miles away. So what tiny changes unleashed the tornado of human history?
Many different features make up the human package, from dexterous hands to large brains and sociability. But what makes us radically different is our collective control of information about our surroundings. We don’t just gather information, like other species. We seem to cultivate and domesticate it, as farmers cultivate crops. We generate and share more and more information and use it to tap larger and larger flows of energy and resources. New information gave humans improved spears and bows and arrows that allowed them to hunt larger animals more safely. It gave them better boats that gave them access to new fisheries and new lands, and it offered new botanical knowledge that allowed them to leach the poisons from potentially edible plants such as cassava. In more modern times, new information lay behind the technologies that let us tap the energy of fossil fuels and build the electronic networks that link us into a single world system.
Information management on this scale was not the achievement of individuals. It depended on sharing, on the accumulation of millions of individual insights over many generations. Eventually, community by community, this sharing created what the Russian geologist Vladimir Vernadsky called a noösphere, a single global realm of mind, of culture, of shared thoughts and ideas. “There is,” writes Michael Tomasello, “only one known biological mechanism that could bring about these kinds of changes in behavior and cognition in so short a time.… This biological mechanism is social or cultural transmission, which works on time scales many orders of magnitude faster than those of organic evolution.” This process, which Tomasello calls “cumulative cultural evolution,” is unique to our species.14
The tiny change that allowed humans to share and accumulate so much information was linguistic. Many species have languages; birds and baboons can warn others in their group of the approach of predators. But animal languages can share only the simplest of ideas, almost all of them linked to what is immediately present, a bit like mime (imagine trying to teach biochemistry or wine-making in mime). Several researchers have tried to teach chimps to talk, and chimps can, indeed, acquire and use vocabularies of one or two hundred words; they can even link pairs of words in new patterns. But their vocabularies are small and they don’t use syntax or grammar, the rules that allow us to generate a huge variety of meanings from a small number of verbal tokens. Their linguistic ability seems never to exceed that of a two-or three-year-old human, and that is not enough to create today’s world.
And here’s where the butterfly flapped its wings. Human language crossed a subtle linguistic threshold that allowed utterly new types of communication. Above all, human languages let us share information about abstract entities or about things or possibilities that are not immediately present and may not even exist outside of our imagination. And they let us do this fast and efficiently. With the partial exception of honeybees, whose dances can tell other bees where to find honey, we know of no animals that can transmit precise information about what is not right in front of them. No animal can swap stories about the future or the past, or warn about the lion pride ten miles to the north, or tell you about gods or demons. They may be able to think about such things, but they cannot talk about them. And that may be why it is hard to find any evidence for teaching within any other species, even among our closest relatives, the monkeys and apes.15
These linguistic enhancements allowed humans to share information with such precision and clarity that knowledge began to accumulate from generation to generation. Animal languages are too limited and too imprecise to allow this sort of accumulation. If any earlier species did have this ability, it would surely have left traces, including an expanding range and an increasing impact on its environment. In fact, we would see the sort of evidence we find for human history. Human language is powerful enough to act like a cultural ratchet, locking in the ideas of one generation and preserving them for the next generation, which can add to them in its turn.16 I call this mechanism collective learning. Collective learning is a new driver of change, and it can drive change as powerfully as natural selection. But because it allows instantaneous exchanges of information, it works much faster.
How and why our species acquired the linguistic power needed to unleash this powerful new driver of change remains unclear. Was it, as American neuroanthropologist Terrence Deacon has argued, a new ability to compress large amounts of information into symbols (deceptively simple words like symbol that carry a huge informational cargo)? Or was it the evolution of new grammar circuits in the human brain that helped us combine words according to precise rules so as to convey a great variety of different meanings, as the linguist Noam Chomsky has suggested? This is a tempting idea because, as another linguist, Steven Pinker, puts it, the really difficult trick was “to design a code that can extrude a tangled spaghetti of concepts into a linear string of words” and to do this so efficiently that the hearer could quickly re-create the spaghetti of concepts from the linear string.17 Was human language enabled by the increased space for thinking available in an enlarged cortex, which could hold enough complex thoughts in place to form syntactically complex sentences or let an individual memorize the meanings of thousands of words?18 Or do improved forms of language have their roots in the sociability and willingness to collaborate that is particularly well developed in our own species?19 Or was there perhaps a synergy between all these drivers?
Whatever happened, our species seems to have been the first to cross the linguistic threshold beyond which information can accumulate within communities and across generations. Like a gold strike, collective learning unleashed a bonanza of information about plants and animals, about soils, fire, and chemicals, and about literature, art, religion, and other humans. Though some information was also lost every generation, in the long run, human stores of information accumulated, and that growing wealth of knowledge would drive human history by giving humans access to increasing flows of energy and increasing power over their surroundings. Here is how this mechanism is described by a pioneer of the study of memory, the Nobel Prize winner Eric Kandel:
Although the size and structure of the human brain have not changed since Homo sapiens first appeared in East Africa… the learning capability of individual human beings and their historical memory have grown over the centuries through shared learning—that is, through the transmission of culture. Cultural evolution, a nonbiological mode of adaptation, acts in parallel with biological evolution as the means of transmitting knowledge of the past and adaptive behaviour across generations. All human accomplishments, from antiquity to modern times, are products of a shared memory accumulated over centuries.20
The great world historian W. H. McNeill constructed his classic world history The Rise of the West around the same idea: “The principal factor promoting historically significant social change is contact with strangers possessing new and unfamiliar skills.”21
Living in the Paleolithic
Human history begins, then, with collective learning. But when did collective learning begin?
Even our alien scientists would hardly have noticed the first flickering of collective learning as they circled Earth two hundred thousand years ago. Some form of collective learning may have been at work even in H. erectus communities, but its consequences were not yet revolutionary. Hints of more rapid technological change begin to appear in the African archaeological record at least three hundred thousand years ago in the form of increasingly delicate stone tools, many of them hafted.22 And it is not just Homo sapiens who show this creativity but also Neanderthals and the hominin species known as Homo heidelbergensis. Perhaps all these species were acquiring improved forms of language that brought them tantalizingly close to threshold 6. Early evidence of ritual or symbolic or artistic activity is particularly significant because it suggests an ability to think symbolically or tell stories about imaginary beings, and that may indicate the arrival of modern forms of language.
Perhaps there was room for only one species to cross the threshold to collective learning. There is an evolutionary mechanism known as competitive exclusion that explains why two species can never share exactly the same niche. One will eventually drive out its rival if it can exploit the same niche slightly more effectively. So we can imagine several species gathering near the evolutionary threshold to collective learning, but then one broke through and began to exploit its environment so efficiently that its numbers multiplied and grew fast enough to lock out its rivals.23 This may help explain why our closest hominin relatives, such as the Neanderthals, have perished, and our closest surviving relatives, the chimps and gorillas, are approaching extinction.
Evidence of technological and cultural change from before a hundred thousand years ago is foggy and difficult to interpret. Our own lineage began to spread within Africa starting at least two hundred thousand years ago, which may point to the advantages of collective learning.24 But in a world of small, scattered communities, most of them little larger than extended families, change was slow, erratic, and easily reversed. Whole groups could die out suddenly, along with the technologies, stories, and traditions they had built up over many centuries. The largest catastrophe of this kind occurred about seventy thousand years ago. Genetic evidence shows that the number of humans suddenly fell to just a few tens of thousands, only enough to fill a moderate-size sports stadium. Our species came close to extinction. The catastrophe may have been triggered by a massive volcanic eruption on Mount Toba in Indonesia that pumped clouds of soot into the atmosphere, blocking photosynthesis for months or years and endangering many species of large animals. But then human numbers began to increase again; humans spread more widely, and the machinery of collective learning roared into life once more.
In the past one hundred thousand years, we get some glimpses of how our ancestors lived and find clearer evidence for collective learning. Like all large animals, our ancestors collected or hunted resources and game from their surroundings. But there was a crucial difference between those animals and early humans. While other species hunted and gathered using a repertoire of skills and information that barely changed over the generations, humans did so with increasing understanding of their environments, as they shared and accumulated information about plants, animals, seasons, and landscapes. Collective learning meant that, over the generations, human communities hunted and gathered with growing skill and efficiency.
Some sites give us intimate glimpses of how our ancestors lived. At Blombos Cave, on the Indian Ocean shores of South Africa, archaeologist Christopher Henshilwood and his colleagues have excavated sites dating from ninety thousand to sixty thousand years ago. The inhabitants of Blombos Cave ate shellfish, fish, and marine animals as well as land mammals and reptiles. They cooked in well-tended hearths.25 They made delicate stone blades and bone points that were probably hafted to wooden handles with specially prepared glues. But they were also artists. Archaeologists have found ocher stones with geometrical scratch marks on them that look for all the world like symbols or even writing. They also made different-colored pigments and ostrich-shell beads. It is tempting to see this evidence as a sign that the Blombos communities valued collective learning and the preservation and transmission of information, and that surely means that they preserved and told stories that summed up their community’s knowledge.
It is hard not to see similarities with modern foraging communities. If these similarities are not misleading us, we can imagine many groups like those from Blombos Cave with a great diversity of gathering and hunting techniques built up over many generations. We can imagine them migrating through familiar home territories, held together by family ties and shared languages and traditions. They surely danced and sang, too, and told origin stories, and they almost certainly had what we moderns might want to call religions.
At the Lake Mungo site in Australia, the evidence for religion is compelling. A cremation and burial from about forty thousand years ago and a scattering of other human remains are evidence of rich ritual traditions. Other evidence from the site reminds us that Paleolithic societies, like modern human societies, underwent profound upheavals, many caused by the unpredictable climate changes of the most recent ice age. There were regular periods of aridity from the moment humans first arrived in the Willandra Lakes Region, perhaps fifty thousand years ago. About forty thousand years ago, aridity increased and the lake system began to shrink.
Twenty thousand years later, at the coldest phase of the ice age, there were communities living in tundra-like environments on the steppes of modern Ukraine. At sites like Mezhirich, people built huge marquee-like tents, using skins stretched over a scaffolding of mammoth bones, and warmed them with internal hearths. They hunted mammoths and other large animals and stored meat in refrigerated pits for recovery during the long cold winters. They hunted fur-bearing animals and used needle-like objects with ornamental heads carved from bone to sew warm clothing. As many as thirty people may have lived together at Mezhirich during the long ice-age winters. There are similar sites near Mezhirich. This suggests there were regular contacts between neighboring groups, the sort of networks through which information about new technologies, changing climates, animal movements, and other resources would have been exchanged, as well as stories. People, too, would have moved between neighboring groups.
The remains left behind by Paleolithic communities offer grainy snapshots of their societies. But each snapshot represents an entire cultural world, with stories, legends, heroes, and villains, scientific and geographical knowledge, and traditions and rituals that preserved and passed on ancient skills. This accumulation of ideas, traditions, and information was what allowed our Paleolithic ancestors to find the energy and resources they needed to survive and flourish and migrate farther and farther in a harsh, ice-age world.
