Intelligence is sometimes measured by the number of cortical neurons in the brain, a more precise measurement than simple brain volume. Human beings have about 11.5 billion cortical neurons, more than any other species. Chimpanzees are in second place with about 6.2 billion, and bottlenose dolphins are in third with about 5.8 billion.
An alien biologist visiting from a distant planet might look at the remarkable similarities in our physiology and conclude that chimpanzees would live pretty much as humans do, only more simply.
But there’s something definitively, well, human about us.
Chimpanzees and dolphins live pretty much as they did 100,000 years ago, so far as we can tell. Not so Homo sapiens. Until just 20,000 or 30,000 years ago, the evidence suggests, humans lived as the animals live, browsing for fruit, nuts, small prey and carrion. But we were different. We had technology.
The earliest stone tools belonging to the ancestors of Homo sapiens appear to be about 3.4 million years old. They were simple: rocks chipped to create sharp edges. For a long time that was the limit of human technology. Somewhere along the line we learned to attach stone points to wooden shafts, inventing the spear and the arrow. It appears that technology progressed very, very slowly for a very, very long time. Humanity didn’t make any big lifestyle changes, so far as we can tell from the archaeological record, until about 40,000 years ago when we started wearing jewelry, painting on cave walls and playing little flutes made of bone.
There is, of course, no way of knowing what the first flute-playing, necklace-wearing cave-dweller was thinking, but based on our knowledge of human nature an informed person can guess at the sequence of thought that led to the acceleration of human technological development.
We first migrated out of Africa about 10,000 years before we had flutes, necklaces or, as far as we can tell, clothes. We discovered that most of the world was relatively cold. Or very cold. You can’t wander very far north of the Mediterranean Sea naked, on foot, before winter makes its frigid potential known. Europe is more enjoyable in December if you grow a nice coat of fur, or make one. For us, technology was the answer. No trace of the first human clothing has been found, but we can guess that the earliest Homo sapiens immigrants to move north invented the first suit.
The next thing you know we needed matching belts and handbags.
It seems there were already humans living in Europe when we, Homo sapiens, arrived from the south. Homo neanderthalensis, Neanderthals, had lived in Europe for about 100,000 years before we arrived and were, evidently, comfortable and successful in the cold, dark forests of the northern continents. Neanderthal brains were just as large, possibly larger, than ours. For a long time anthropologists thought the Neanderthals were our ancestors but recent DNA studies indicate that they were probably a completely separate species very like us but adapted to life in the north. It seems probable, based on the DNA evidence, that the two species of human rarely interbred. Africans carry no Neanderthal DNA. In northern races, between 1 percent and 4 percent of a person’s genes might have come from Neanderthals. Neanderthals were about our height, but much stronger. Based on their heavy bone structure, scientists think they might have been twice as strong as today’s professional football players. They were almost exclusively carnivorous, while we Homo sapiens were more omnivorous.
The Neanderthals disappeared about 30,000 years ago. Scientists debate the cause of their extinction but it seems pretty likely that we either out-competed them for resources or wiped them out in interspecies conflict. This is a controversial topic. However, our technological superiority to the Neanderthals is not so controversial. Not long before the disappearance of the Neanderthals archaeologists have documented our species’ “Great Leap Forward,” in which we replaced our old tools with a bunch of new and improved models. Neanderthal technology did not change over the same time period, so far as the scientists can tell. Where we can separate contemporaneous Homo sapiens artifacts from Neanderthal artifacts, we find that Homo sapiens had more varied, highly developed and destructive technology at their disposal.
Needless to say human beings have killed each other by the millions since the disappearance of the Neanderthals. With each generation we wage war in more inventive and devastating ways. The destructive power of our technology advances in step with its redemptive power.
The archaeological evidence combined with the more recent historical record indicates that technology was Homo sapiens’ ticket out of Africa and that, when we encountered a strong, competitive human species in Europe and western Asia we characteristically went about protecting our expanding interests using superior technology.