The Story of the Universe and Me: Where Did I Come From?
Part 7: Us
Human beings, the anatomically modern kind, have lived on Earth for the last quarter of a million years. Although that is a tiny amount of time compared to the vast spans I’ve described so far, I feel we’ve achieved rather a lot.
Humans originated in East Africa, and were very quick to spread across that continent. Our great intelligence and social ability served us well as hunter-gatherers. We developed complex communication, which we now call language. A creative extension of our tool-use and cognitive abilities became culture. Cave paintings and bone or wood sculptures became the first art. Although we might not have been the first animals with imaginations, we were certainly the first to express them with such zeal. Teachings, beliefs and thoughts passed from one generation to the next, establishing the first examples of cultural memory.
Depending on your ethnicity, this is where our stories may diverge for the first time. Up until now, I masked this series as a history of the universe. Really, I was writing a history of me. I aimed to trace the origins of the matter and genes that make me up as far back as I could. Up until now, that story has coincided with the story of every other human. But the spread of our species across and away from Africa led to the isolation and diversification of several groups. Of course, there has been a lot of mixing between these groups throughout human history (to our benefit) and it’s likely that I could lay claim to a far wider ancestry than I’m aware of. But to my knowledge my heritage is almost completely from the British Isles, with just the barest hint of Aboriginal Australian. So those are the paths I’ll be tracing closely.
Isn’t that pretty Eurocentric? Yep, very, but that’s only incidental to the throbbing egocentrism of this whole series.
After conquering our home continent, humans began to emerge into South Asia about 70,000 years ago. As little as a few hundred individuals began this journey, leaving the majority of humanity in Africa. In fact, the wide array of ethnicities thought of as African contain more genetic diversity, even today, than the rest of the world combined.
Of course, humans are pretty good at breeding, so that handful of early settlers grew in number as they spread. They out-competed other hominids like Homo erectus, who had themselves spread from Africa much earlier. We drove them to extinction, although it’s possible we interbred with them first.
A group of these settlers made their way across the South Asian coastline over the next ten thousand years or so. There was still an Ice Age in effect, so sea levels were much lower than today. That made their journey much easier as they travelled through South-East Asia and onto the islands now known as Indonesia. This wouldn’t have been possible without boats, making these explorers some of the earliest mariners. From there, they found their way to Australia, either via Timor or New Guinea, the latter of which was still connected to the continent. By 40,000 years ago, and possibly earlier, they had arrived. They, one arm of my distant ancestors, proceeded to spread to every corner of the continent.
Humans also spread to East Asia 30,000 years ago, and up via Siberia and the frozen Arctic into North America by fourteen thousand years ago. After that icy trek, the march down to South America was trivial. All of these early colonisations, including Australia, were followed by extinction events, especially of large animals. The megafauna of the continents were ill-prepared for such an intelligent predator.
Another branch of the exodus from Africa reached into Europe over the Zagros Mountains 50,000 years ago, only to find that they had been beaten there. Neanderthals were a distinct subspecies of Homo sapiens that left Africa 300,000 years ago, long before anatomically modern humans. They were better adapted to Europe’s colder climate. The newcomers, called Cro-Magnons, almost definitely interbred with Neanderthals to a small degree. They may also have introduced African diseases to which the Neanderthals were vulnerable, and out-competed them with more proficient society and tool-use. Climate change probably also played a role. However it happened, by 35,000 BCE Cro-Magnon had spread across most of Europe, while Neanderthals had retreated to southern Spain and Portugal. Before long they dwindled to extinction.
Humans were well-established in the British Isles by then, and retained a hunter-gatherer lifestyle. They remained that way for a good thirty thousand years, until, somewhat behind the rest of Europe, agriculture found its way there.
The importance, for good or bad, of agriculture in human history cannot be overstated. The deliberate cultivation of plants and, later, animals for food allowed us to give up our nomadic lifestyle to settle in a single location. With that came permanent settlements and greater security, allowing our populations to swell. It also brought about more pronounced social strata, with division of labour encouraging the emergence of an organisational upper class and a labouring lower class.
Agriculture introduced a brand-new evolutionary force to the world: artificial selection. Instead of being selected by environmental factors for traits that allowed them a better chance of survival, many organisms were now being selected and bred for properties that made them more useful to us. It works identically to natural selection, except that humans make deliberate choices about which domesticated individuals to protect and which get to reproduce. Hence, the process is much faster and frequently results in species that are dependent on humans to survive. To this process we owe the existence of dogs, modern cattle (the wild ancestors of whom, aurochs, are long extinct), apple trees that produce larger and tastier fruit than any that ever existed naturally, hens that lay eggs every day, and orange carrots. Artificial selection extends to every single species farmed by humans. It transformed the meagre fare that we gathered as nomads into species that feed billions of people with their output. It’s the original genetic engineering, and we’ve been doing it for millennia.
From the permanent settlements that agriculture enabled, we saw the first civilizations emerge. Of course, Britain and Ireland remained well behind the rest of Eurasia in this respect, being in an isolated corner of the world. While empires were budding around the Mediterranean, in northern Africa, southern Europe and East Asia, people in the Isles were still learning to craft tools out of bronze (2500 BCE) and later iron (800 BCE).
Britain experienced its first taste of imperialism - of which it would later become one of the great masters - in 40 CE, when its southern half became a province of the Roman Empire.
To be continued!