What’s an origin story?

Where do we come from? How was our world created? Humans have always asked these sorts of questions. Throughout history, every culture has come up with their own answers. We call these origin stories. An origin story is a way of explaining how something began. The story might be about the origin of a group of people, humanity, the world, or even the whole Universe. Origin stories are important because they help us understand our place in the world, where we come from, and where we’re going. Today, historians, scientists, religious leaders, and others continue to provide new answers to these questions.

What follows is an origin story from the perspective of Big History. It attempts to tell the story of how we got here by beginning at the beginning: the very origins of our Universe. This story is grounded in scientific evidence. However, it’s not the only way to answer questions about our origins, and even this Big History origin story is constantly changing with each new discovery and innovation. We can use this origin story to help us see how everything is connected—from tiny atoms to vast galaxies, from ancient plants and animals to humans who tell stories and build cities. This big-picture view can help us understand the past and our world today, as well as think about what might happen in the future.

Big History origin story

In the beginning, as far as we know, there was nothing. Suddenly, from a single point, all the energy in the Universe burst forth. We call that moment, which scientists believe happened about 13.8 billion years ago, the Big Bang. Since the Big Bang, the Universe has been expanding. It’s also been cooling down, because at first, after that enormous burst of energy, things were very hot.

It was so hot, there was no matter in the Universe at all. (Matter is a way of describing stuff that takes up space and has mass.) A few hundred thousand years after the Big Bang, the Universe cooled down enough that the first matter formed. This was possible because with cooler temperatures, one electron could stay in orbit around one proton to become an atom of hydrogen. All matter is made of atoms.

For millions of years, clouds of hydrogen atoms and helium atoms swirled around space. The Universe was a very dark and very simple place. Then, about 200 million years after the Big Bang, gravity pulled enough atoms close enough together that they heated up and began to burn as stars. Gravity eventually pulled these first stars together in giant clusters called galaxies.

After some stars burned up all their matter, they died in huge explosions. The explosions of dying stars generated so much heat that some atoms fused together, becoming more complex and forming new elements, including carbon, iron, oxygen, and silicon.

As stars died, they scattered clouds of gas across the Universe. These clouds contained all the elements needed to make planets and moons and everything around you today. About 5 billion years ago, gravity pulled about 99% of the atoms from an exploding star together to form a new star, our Sun. The leftover 1% of matter stuck to each other and formed eight planets, which all revolve around the Sun. This is our Solar System.

The third closest planet to the Sun is Earth—our home. It was the perfect size—not too big, not too small. And it was the perfect distance from the Sun—not too far, not too close. A thin crust formed over Earth’s hot interior, and the temperature was just right for water to form vast liquid oceans on the crust. Gradually, chemicals formed in the oceans and combined and got more and more complex until single-cell living organisms appeared that were able to maintain themselves and reproduce. For 3 billion years, these one-celled creatures reproduced almost—but not quite—exact versions of themselves. Over many generations, they gradually changed in response to their environment.

Life becomes more complex

As living things changed and got more complex in response to their environment, they also started to have an impact on the environment itself. Some changed in ways that let them use energy from the Sun, and they released oxygen into the atmosphere. The oxygen formed an ozone layer around the planet that protected life from the Sun’s rays.

Eventually, cells stuck together to make creatures with many cells. Plants and animals came out of the sea and onto land and became ever more complex. Then, about 2.8 million years ago, the first species of human beings evolved from a shared ancestor of modern apes. About 250,000 years ago, our species—Homo sapiens—evolved from these early human ancestors.

Homo sapiens could communicate with language. They could sing, dance, draw, and cooperate better and in larger numbers than other animals. They had big brains. Humans learned to pass on their learning to their children so that each generation got more skilled and had better tools, which helped them hunt animals and gather plants for food.

Then, about 12,000 years ago, some humans learned to grow their own food and herd their own animals. They learned to farm. This gave humans new sources of food and energy, so they could live in larger and larger groups. These groups expanded into cities, where some people could do jobs other than making food. Some cities expanded into vast empires, and some became centers of learning and innovation. Humans developed more-powerful technology and more-complex societies. They traveled, traded, and shared inventions with each other.

As human populations grew, they used more and more of Earth’s resources. People were always looking for more sources of energy to use to support their increasingly complex lives. About 300 years ago, humans learned to use the energy from coal to power machines. Coal is made from dead trees that were buried underground for hundreds of thousands of years. Humans also learned to burn oil, which comes from plant and animal remains buried long ago under the sea. Using these fossil fuels to power machines, humans began to change Earth’s climate quickly, as the gases released from burning these fuels collected in the atmosphere.

Now humans are in a predicament: Our population is increasing rapidly, fossil fuels are running out, we are pushing many plants and other animals into extinction, and we are changing the climate. What are we going to do next?