In his 2012 book "The Social Conquest of the Earth," Edward Wilson described humans as eusocial apes[13]. Our divisions of labor, overlapping generations, and cooperative care of young give us a "superpower" that few other species can achieve.
Humanity did not evolve in a garden of Eden. Severe climate shifts hammered us, over and over. We survived through many near-extinction bottlenecks, down to a few thousand individuals, over and over. These events didn’t kill us off. Like the Argentine ants, we are descended from a single small population of genetically similar people. This lets us recognize each other as members of the same tribe.
We survived disaster after disaster by working together. We developed the ability to pass knowledge down the generations. We evolved altruism, the spreading of risk through tribes and generations.
Early altruistic humans had many cheats: scavengers, parasites, and above all, other humans. For every social instinct we evolved, we evolved talents for cheating others. And as cheats got smarter, social humans got better at identifying and punishing them.
Humans form networks of relationships. Sometimes these are hierarchical. More often we form ties to other individuals and groups. Those relationships aren’t arbitrary. They build on meticulous accounting. We calculate trade in genes, food, shelter, sex, affection, information, time. It is mostly subconscious, yet it is constant and dominant.
We have sophisticated mental tools to track these relationships. We can remember faces for a lifetime. We remember the good and the bad, in detail. We can guess the relative value of any favor or item, in a given place or time. That roast chicken you shared with me for lunch is worth three beers tomorrow, or one in two weeks' time. We remember cheats forever, and we do not forgive them.
We have imagination, so we can plan how to work together. We have language, to exchange knowledge. We express our emotions on our faces, voices, body language, and the blush of blood on our face, ears, and body.
All of these are adaptations to defend against cheats. Just as the ant colony is the product of an arms race, so is human society. Who we are stems from this endless war between working together, and that promise: "the check is in the mail!"
The Forever War
You and me, we’ve been at war since before either of us even existed. — John Conner, in Terminator Salvation
Since we’re talking about evolution and a long arms' race, one question pops up. That is, when did human psychopathy start to evolve? What time period are we looking at here? It is a question no-one else has ever asked, according to Google. I’m going to try to answer it.
First, we can rule out a recent origin. Psychopathy is a consistent feature of humanity across the world. It is a human universal. It thus predates our expansion out of Africa, some 150,000 years ago.
The origins of humanity keep getting pushed back in time. The ritual burial cave of homo naledi in South Africa dates from around 3 million years ago. The oldest stone tools go back 3.3 million years[14].
Ritual burials speak of empathy for the dead, and social emotions that go beyond tribe and family. Stone tools point to a structured society, a division of labor, some level of trade, and forward planning.
Let me explain. To turn stone into usable tools takes incremental skill and learning, adapting techniques that follow a slow evolution. This means knowledge passing down the generations, which means specialized individuals, a caste of tool makers.
As Scientific American writes,[15]
The Lomekwi knappers were able to deliver sufficient intentional force to detach repeatedly series of adjacent and superposed flakes and then to continue knapping by rotating the cores. [They] intentionally selected big, heavy blocks of very hard raw material from nearby sources even though smaller blocks were available. They used various knapping techniques to remove the sharp-edged flakes from the cores.
The raw materials are not widespread. The toolmakers had to travel to locations with the right rocks. They had to make their tools. They had to carry those tools back to people who needed them. This meant taking food and water, sacks or ropes, and so on.
It also means the ability to plan in advance and organize with others. This means language, rich enough to express futures and maybes. This sounds advanced for hominids with small brains, until you realize that ants do much the same. This behavior does not need to be conscious. It can be instinctive.
A stone tool production chain has cores, flakes, and anvils. It goes far beyond the mental capacity of a single individual. It tells us there was a social structure. Some specialized in making tools. Others in using the tools for hunting, cleaning meat, breaking bones, cutting wood. Such a social structure means altruism, that is, the ability to share with others. And whenever there is altruism, there are cheats.
The counter-notion is that early humans were generalists, and that they made their own tools as they needed them. Specialization and trade comes much later, in this view. Yet it’s an easy model to discredit. Hunting demands its own sets of specialized skills. There would be extreme competition on men to be the best hunter, or the best tool maker. Women need tools as well as men, yet are unlikely to be toolmakers. Two specialists able to trade can always do better than two generalists. So the generalist model does not survive sexual selection, nor economics, nor the male-female division of labor.
So I think we can date human psychopathy to at least 3 million years ago.
The Puzzle of the Big Brain
Our most distinctive human feature is our over-sized brain. The fossil record shows it suddenly growing larger and larger, starting around two million years ago. What drove this expansion? The answer turns out to be: other people. As David Geary says[16]:
There was very little change in brain size across our sample of fossil skulls until we hit a certain population size. Once that population density was hit, there was a very quick increase in brain size.
Why would more people mean bigger brains? Geary credits "social competition", with more people competing for the same food supply. The smartest win, have more kids, and the genes for smaller, stupider brains die out, he argues.
Yet human food supply is not a static resource. Rather, it is a direct result of human activity. More people means more food, not less. Fish do not line up in shallow water, waiting for someone to collect them. Deer do not come in packets of twelve. Food fights back. It is a deep and complex puzzle, solved by technology, knowledge sharing, altruism, and trading. Our social model gets more, not less, effective with more people. So, the more people, the more food.
This only stops being true when we hit the limits of our environment. That is, during a population collapse, not a boom. Only in catastrophic situations do people compete for food.
We could also ask why intelligence should win food? It does not happen in other animals. Big brains are expensive and dangerous, for mother and baby. Why not evolve larger teeth, or stronger muscles, or longer legs? It seems arbitrary to claim intelligence as the key to getting more food, without further explanation.
We can make Geary’s model work, if we replace "social competition" with "arms race between altruists and cheats." When populations consist of small, isolated families, cheating is a poor strategy. It is easy to detect and punish cheats. Predators need a certain population density. They must be able to move on after exhausting a given territory.
14
http://www.the-scientist.com/?articles.view/articleNo/43066/title/Oldest-Stone-Tools-Discovered/
15
http://blogs.scientificamerican.com/observations/archaeologists-take-wrong-turn-find-world-s-oldest-stone-tools-update/