The big question for this segment is, does human history represent a new level of complexity in the history of the Earth? [MUSIC] We humans obviously represent a sort of pinnacle of complexity, right? Well, maybe not. In evolutionary terms, we appeared a split second ago. And we live on an obscure planet, orbiting a pretty average star, which is one of several hundred billion stars, in a pretty average galaxy, which is one of several hundred billion galaxies in the universe. And yet, there really is something very odd about humans and about human history. Today the more than 7 billion humans on earth represent a force for change that is moving more earth than the winds and rain and rivers. We're transforming the mix of organisms on planet Earth, we're even transforming the global climate system. Our power depends on collaboration, through intricate networks of language, writing, religion, custom, trade, and electronic communications that link all humans into a single system, whose tentacles reach into every corner of the earth. That network system is itself astonishingly complex. But it's also linked in even more complex ways, which we do not fully understand, to deeper processes. Such as the cycling of carbon and nitrogen between the atmosphere and the Earth's crust. Furthermore, we seem to be the first species in almost 4 billion years of life on Earth that has had such astonishing power. So something very odd has happened. And the moment we're living through today counts as a major turning point in the history of the biosphere. So what happened? Why are we humans so powerful? There is no universal agreement about what makes us humans so unique, but there is a broad consensus that the difference has something to do with language. For reasons we don't fully understand, the first humans who appeared perhaps 200,000 years ago were able to communicate with an entirely new level of precision. Humans acquired a capacity for what some scholars have called symbolic language. Many organisms have simple forms of language, but they seem to be able to communicate only about what is immediately present. Hide, there's a lion. Or, watch how I pull termites out of this mound. Humans use words as symbols, which like compressed files on a computer contain huge amounts of information. So that a lot of information can be passed from brain to brain. And it can be passed very fast. If I say, pink elephant. Think of the number of ideas, associations, questions, images that that simple phrase puts into your brain. And curiously, it plants in your brain the idea of something that doesn't exist and has never existed. So, humans can discuss abstractions, things that aren't present in front of us. They can discuss what happened yesterday and they can invent stories and imagine gods and demons. So what changed in the human brain? We don't really know. Perhaps there was a minor rearrangement of the neurons in the human brain. Or perhaps the large human brain provided the memory buffers needed to transmit information in larger amounts. Whatever happened, the consequences were transformative. Because now there existed a creature whose members could share information in such huge quantities and with such precision that information began to accumulate from generation to generation. We are the first species in the history of planet Earth, in which later generations usually know more about their world than earlier generations. This is collective learning, learning at the species level. And collective learning mattered because humans, like all living organisms, use information about the surroundings to generate the energy and resources they need to survive. So that more information meant more energy, more resources, more power over the biosphere. Of course not all that information that accumulated was useful. Jokes accumulated, stories, fashion styles. But some of it was useful and gave our ancestors increasing power over their environments. At first, for more than 100,000 years, information accumulated slowly in small isolated, nomadic communities, but eventually began to accumulate faster. As humans got better at extracting the resources they needed to support larger communities. Things changed fast from 10,000 years ago, after the last Ice Age, when humans started to farm. Farming could support much larger populations, so now humans began to gather in huge settlements of thousands, and eventually millions of individuals. Who are exchanging a colossal amount of information about how to manage and exploit their surroundings. These huge communities also became more diverse and more complex as they were divided by language, by religion, by wealth, and by power. Module five gives us just a few glimpses into crucial stages in this long process of human history, during which humans created more and more complex societies. Until eventually they had created the staggeringly complex and powerful world of the Anthropocene. [MUSIC]
