When I wrote my big essay, more than half of it covered the eons before humans arrived on the evolutionary scene. My studies over the past decade have emphasized the human journey. It is all fascinating, but the story naturally began focusing on humans, as we dominate Earth like no other animal ever did.
The combination of climate changes, as Earth cooled down to our ice age, and evolution led to apes that left the shrinking tropical canopies, to later invade the growing grasslands. Somewhere along the line, some apes became bipedal, at least four million years ago. Chimps and bonobos are our closest evolutionary cousins, and it is easy to see how many human behaviors have their roots in our ape heritage, including the predilection for violence. My conception of the human Epochs begins with the first crafted stone tools yet found, at about 3.3 million years old. It is no coincidence that the human line’s brain began growing then, as brains are energy hogs. Those tools always primarily had an energy function, to enhance food availability in the earliest days, and giant tortoises were among the first to go, as they had no defense against rock-wielding apes.
When Homo erectus appeared on the evolutionary scene a little more than two million years ago, its brain was twice the size of a chimp’s, and human evolution since then has been relatively modest. With a few facial prosthetics, a Homo erectus could walk down a street and not elicit much comment. The debates are heated today on just when humans controlled fire and invented language, which Darwin said were humanity’s two greatest feats. They both may have arrived around when Homo erectus did. Within 700,000 years of Homo erectus’s arrival, vast changes began happening, including the extinction of many species of African and Asian megafauna, especially members of the elephant family, which was the most successful family of mammals before the rise of humans.
The human journey has primarily relied on three factors:
1. Our ever increasing levels of energy consumption;
2. Increasing intelligence, both individually and collectively;
3. The rise of tools, which continually became more sophisticated.
The dramatic changes of our ice age certainly had profound effects on the human journey, including evolutionary changes. Humans are the only highly intelligent mammals for which fathers play any kind of social role. Women are experts in motherhood, after many millions of years of evolution, while men are still figuring out fatherhood. Women have evolved to produce healthy and reproducing offspring, while men have evolved to form military organizations to fight neighboring societies. We live with these evolutionary trends to this day.
In the hunter-gatherer phase of the human journey, it is quite possible that psychopathic genes were culled from the gene pool, although that is relative. Chimps are hundreds of times more aggressive and violent than humans are.
Homo sapiens, Neanderthals, and Denisovans were arguably all members of the same species, as they interbred. A trend in my lifetime has been for scientists to increasingly attribute high intelligence and sophisticated toolsets to Neanderthals. But Homo sapiens somehow reached a threshold of intelligence called behavioral modernity, likely sometime between 100,000 and 60,000 years ago. Perhaps the leading hypothesis is that was some kind of hyper-social phenomenon, which allowed for a comparative “Great Leap Forward.” Behavioral modernity allowed humans to conquer Earth, which is what I call the Second Epoch of the human journey, and which comes next.