Introduction

Everything on Earth has a history. You have a history, and so does the carpet in your living room. There’s a history of the planet and even a history of the entire universe.

Big History is the story of the entire universe. This article explains two ways of telling Big History.

Thresholds of Increasing Complexity: David Christian’s Big History

David Christian is a historian. He studies the stories people tell about the history of humans. Every culture has an origin story that explains where we come from.

There is no one origin story for everyone on Earth. Christian claims that one has been emerging over the last 50 years. He calls this “Big History.”

Christian says that sometimes completely new and more complex things comes into existence. They are called complex phenomena. The new phenomena have more parts. Think of it like building with Legos. The large tower you build is more complex than two connected Legos. The tower is a more complex phenomena.

At certain points, phenomena become more complex. This is like the moment when your Lego tower reaches a certain height. Christian found eight important points in the history of the universe. At each point, major changes happened. Together they tell a Big History of the universe. Christian refers to these points as Thresholds.

So, what’s the story?

The story begins with the beginning of the universe: the Big Bang. This was the moment when the universe first began. Then, stars and galaxies emerged in Threshold 2. This was followed by more complex and heavier elements (Threshold 3). Later our Solar System and Earth (Threshold 4) emerged. About 4.5 billion years ago, our sun and planets of the solar system formed. One of those planets was Earth.

The beginning of life is Threshold 5. The first organisms were single-celled bacteria. More complex life evolved from these single-celled organisms. Now, Earth is home to many different plants and animals. That is another example of more complex things developing out of less complex things.

There are three final thresholds. Threshold 6 is when humans evolved. Threshold 7 is when humans learned how to farm. Threshold 8 is when humans started using fossil fuels. Coal and oil are fossil fuels. They produce energy. These thresholds are three major turning points in the history of humanity.

This story covers the entire history of the universe. It explains how our universe became more complex.

Another Big History story: Walter Alvarez’s Improbable Journey in Four Movements

Not all Big Historians use Christian’s system. Walter Alvarez studies Big History. He created his Big History around four periods: the Cosmos, Earth, Life, and Humanity. For Alvarez, every period has its patterns.

For example, Alvarez says that the Earth has provided “gifts” for humans. These gifts include the element silicone. Humans have used silicone to create many tools. These include early tools and modern computers. This is an example of a pattern across a period.

Alvarez does not focus only on patterns. He also studies rare events. Alvarez and his father discovered that a comet or asteroid wiped out the dinosaurs. This unlikely event led to major changes.

Humans belong to a class of animals called mammals. Dogs and dolphins are also mammals. During the time of dinosaurs, there were not many mammals on Earth. Mammals were very small. Humans could not have evolved if not for the extinction of dinosaurs. Scientists believe a huge comet or asteroid hit Mexico 66 million years ago. This allowed mammals to thrive. Human history depended upon this event. This type of event is important to Alvarez’s Big History.

Alvarez does not create one timeline of Big History. Each of the four periods is separate. Yet they are also part of a connected story.

Alvarez appreciates the path that has led us here. It was very unlikely that we humans would evolve as we have. If not for rare events, we would not exist.

These two stories can explain human history.