David Christian structures his groundbreaking Big History course around eight fundamental thresholds. Each of them is associated with new forms of complexity, and each of which has new emergent properties. Here we will take a high-level look at the eight fundamental thresholds of Big History and the material covered within each.
This is article 2 in the series Big History: How Do We Study Everything That Has Ever Happened?
The Eight Fundamental Thresholds of Big History
The first is the creation of the Universe, Threshold 1, about 13.7 billion years ago. That’s a subject normally discussed within cosmology— the moment of the big bang, and the scientific evidence that allows us to piece together the ever-evolving story of creation.
The second is the creation of the first complex objects, stars. The first stars appeared more than 12 billion years ago, quite soon after the creation of the Universe. They provide the energy and the raw materials for later forms of complexity.
Threshold 3 is the creation inside dying stars of the chemical elements that allowed the creation of chemically complex entities, including planets and including you and me.
The next threshold is the creation of our Earth. And what we look at in that section is the creation of solar systems. Now, these are objects that are chemically significantly more complex than stars. So that’s why this is a new level of complexity. Our Earth was created as a by-product of the creation of our Sun and solar system about 4.5 billion years ago. This threshold also surveys the history of our home planet—and we’re in the territory of geologists.
Threshold 5 is the creation and evolution of life on Earth. The first evidence of life comes from about 3.8 billion years ago on this planet. Now, the creation of life is a threshold that may also have been crossed many times, billions of times before in other parts of the Universe, but as yet we have no firm evidence that this is true. Life, so far, we can only study on our one planet. This threshold also surveys the evolution of our own ancestors, the hominines, from about 6 million years ago.
Then we come to Threshold 6. By Threshold 6 we’re now just 250,000 years ago. We’ve now covered most of 13 billion years, and we’re reaching the present moment. Threshold 6 is the creation of our own species, Homo sapiens, about 250,000 years ago. It argues that we have a capacity to adapt and to change that is unprecedented among other organisms on Earth. We also cover the Paleolithic era of human history—the oldest, the longest, but also the least well-documented part of our history. The Paleolithic era lasts until the appearance of agriculture, 10,000 to 11,000 years ago.
Threshold 7 is the emergence of agriculture and agricultural societies from about 11,000 years ago, and it introduces what I’ll call the Agrarian era of human history, the second of three major eras of human history. Agriculture marked a fundamental change in human history because what it did was accelerate the pace of change. It allowed population growth—the emergence of larger, denser, and eventually more complex societies, including the great agrarian civilizations, such as the Roman Empire or the great empires of China.
And finally we come to Threshold 8, the “Modern Revolution.” This introduces the Modern era of human history. In this part of the course we’ll cover the astonishing series of transformations that have created today’s unified, complex world in just a few centuries, three or four centuries.
Then what we do is widen the lens again to look at the future, look at the future of humans, of the Earth, and eventually of the Universe as a whole. What’s going to happen to the Universe?
Big History provides us the chance to think deeply about the place of human beings and modern society in the larger scheme of things. It offers a clear understanding of the overall shape of what I’m tempted to call a “modern, scientific creation story,” and an understanding of why this story is both important and in some ways very beautiful. Behind the fragmented vision of reality that modern educational systems offer, there is in fact a unified account offered by modern science of reality and its evolution.