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READ: Big History — An Overview

Big History: An Overview

By John Green, adapted by Newsela
History is an attempt to understand both our insignificance and our significance. To study history is to better understand the world and your place in it.
You are very small. You are one of several billion living members of your species, a species that lives on the fifth largest planet orbiting a star we call the Sun. There are more than a hundred billion such stars in our galaxy, and perhaps a hundred billion galaxies in the Universe. It’s almost impossible to grasp your smallness—there are more stars in the Universe than there are grains of sand on Earth.
And yet, you’re also very large. You’re a member of an extraordinarily powerful species that has dramatically reshaped the biosphere, the first species on Earth to understand the vastness of the Universe around it. Your choices—how to organize your community, what to value, what to battle against—shape not just your life but the lives of those around you and the lives of those still to come. And you are physically vast as well: Your body contains trillions of cells, and is colonized by trillions more microscopic organisms.

What Is History?

History is an attempt to understand both our insignificance and our significance. To study history is to better understand the world and your place in it. You, and the other humans with whom you share this world, are the culmination of the human story.

What Is Big History?

There’s a lot more to history than the human story. Let’s consider the world before humans. If you think of history as the story of life on Earth, almost all of it played out before our species (Homo sapiens) showed up on the scene. After all, we’ve been around only for the last 250,000 or so years—less than 0.01% of the history of life on Earth.
From the very beginning, we’ve had different stories that explain the origins of the Universe, our planet Earth, and life itself. These origin stories, as they’re called, are as varied as the cultures that created them. At its heart, Big History is simply another origin story. However, it differs from all other origin stories because it’s science based. Big History uses the information we have available—the scientific evidence—to create an understanding of the Universe.

Thresholds of Increasing Complexity

Because the scale of Big History is so vast (remember, it covers the history of the Universe), it would be impossible for this story to include everything. All historians have to make choices about what to include and what to leave out in the stories they tell. So, what does the story of Big History focus on? Big Historians focus on eight turning points in the history of the Universe, which we call thresholds. These are moments when the Universe became significantly more complex than it had been previously.

Threshold 1: The Big Bang

Modern science suggests that the Universe was created in a “big bang” about 13.8 billion years ago.
The Big Bang was a split second in which all matter and energy expanded at tremendous speed and became the Universe. What was there before the Big Bang? It’s mind-bending to think about, but in some ways, there was no “before” the Big Bang, because the Big Bang created not only space as we know it, but also time as we know it. The important thing to know is that around 13.8 billion years ago, very suddenly, the Universe exploded into being. It’s also important to recognize that although scientists know a lot about the Big Bang, there are still many questions about the details that are being researched.

Threshold 2: The Stars Light Up

After the Big Bang, the Universe expanded and cooled. It took some time (about 380,000 years), but eventually it was cool enough for the simplest atoms, hydrogen and helium, to form. The early Universe consisted almost entirely of hydrogen and helium for a very long time. After a few hundred million years, clouds of hydrogen and helium began to collapse, and the increasing heat and pressure generated by collapse led to the creation of the first stars. Stars represent the second threshold of increasing complexity in Big History. Not only are stars more complex than simple atoms, they’re also able to create tremendous energy. Over time, gravity grouped stars into galaxies, which created further complexity in the Universe.

Threshold 3: New Chemical Elements

Stars made the Universe more complex, but the Universe still consisted primarily of hydrogen and helium. This changed when the first generation of stars died. The death of a star can generate high temperatures and pressures like those in the Big Bang, and this makes possible the creation of more complex atoms. A greater variety of atoms is critical to making more complex things like planets and living things, so the death of stars is the third threshold of increasing complexity in Big History.

Threshold 4: Earth and the Solar System

Our Sun is a star, and like all other stars, it was formed from the collapse of a huge cloud of gas and dust particles. More than 99 percent of this material went to make up the Sun, but wisps of matter orbited around it at various distances. Over time, the matter in each orbit was drawn together by gravity. The gravitational pull created violent collisions into lumps of matter that eventually formed the planets. This process, which we call accretion, is how our Earth was formed approximately 4.5 billion years ago.

Threshold 5: Life

Around volcanic vents at the bottom of Earth’s oceans, complex chemicals engaged in ever-changing reactions powered by the heat from these volcanoes. Those reactions led to the formation of complex chemicals that eventually created the first living organisms. The earliest living organisms consisted of single cells, as most living organisms do even today. Like all living organisms, those early single-celled creatures were subject to the laws of evolution. Generation by generation, the average features of species gradually changed, eventually forming entirely new species.
And for a very long time, that was it: single-celled, microscopic organisms. Life first emerged on Earth perhaps three billion years ago; the first multicellular life didn’t show up until around one billion years ago. But slowly, life grew more and more complex, and large, multi-cellular organisms eventually spread, not only in water, but also on land.
One hundred million years ago, the land-based animals that flourished most were the reptiles we call dinosaurs. About 65 million years ago, however, most of them died off.
Now other types of large animals could flourish in their place. Most successful of all in the last 65 million years has been the large class of animals called mammals.

Threshold 6: Collective Learning

The extinction of the dinosaurs allowed mammals and primates to evolve and eventually dominate the Earth.
Our ancestors, the hominins, are primates, and they first appeared between five and seven million years ago in Africa. Over millions of years, hominins evolved in important ways, both physically and socially. About 200,000 years ago, Homo sapiens, which means “wise human,” appeared. Modern humans developed language, a method of communication that allows them to share complex ideas and pass on knowledge from generation to generation. This process is known as collective learning. In other species, knowledge dies with the generation that created it. Humans have the ability to build on the accomplishments of previous generations.

Threshold 7: Agriculture

Our ancestors lived by foraging. Foragers survive by gathering plants, hunting animals, and scavenging the remains of animals killed by other predators. Foraging supported early humans for millions of years. About 12,000 years ago, humans began to domesticate plants and animals, in other words, to farm. They began interfering with the natural life cycles of plants and animals in order to control where they grew and promote characteristics in those plants and animals they preferred. Growing food gave humans access to a vast amount of energy created by the Sun through photosynthesis. Because foraging for survival was no longer necessary, tremendous lifestyle changes were possible, like settling down to live in cities, creating political structures, and developing skill and trade specializations. The results of all of these changes define the agrarian civilizations. Farming has had a tremendous impact on the way humans live and how they interact with the Earth.

Threshold 8: Modern Revolution

The adoption of farming led to dramatic changes in the way humans lived. Innovation accelerated dramatically with the Modern Revolution, which began about 300 years ago. Rapid growth of human population and the creation of a highly interconnected world are some of the key features of the modern world. These features make the modern world the eighth and final of Big History’s thresholds.

What's Next?

The story of the Universe isn’t only about the past. We know that this story doesn’t end with Threshold 8. So, what’s next? What might the next threshold of increasing complexity be? When you reach the end of this course, you’ll get to use your knowledge of the past to speculate about the future. Because Big History isn’t just about knowing what happened when. Big Historians look across the thresholds to understand the connections between past and present. With that understanding, developing a view of what the future might hold becomes more than a random guessing game. It becomes a way of expressing your own point of view about how the future will be the logical outcome of billions of years of the past.
But let’s not get ahead of ourselves. Let’s really dig into the vastness of what got us here. Remember, you are very small, yet very large. In any other story, this might seem like a contradiction—but not here, not in the Big History story!

Want to join the conversation?

  • purple pi purple style avatar for user louisaandgreta
    “Not only are stars more complex than simple atoms, they’re also able to create tremendous energy. Over time, gravity grouped stars into galaxies, which created further complexity in the Universe.”

    Doesn’t it contradict the first law of thermodynamics to say that stars create energy? And gravity grouped stars into galaxies? Gravity? Doesn’t gravity just happen on planets? And what about dark matter then?

    “In other species, knowledge dies with the generation that created it. Humans have the ability to build on the accomplishments of previous generations.”

    Knowledge is passed on from one generation onto the other no matter the species. Unless the entire group is wiped out all at once then yes knowledge won’t get passed on.
    (4 votes)
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    • boggle blue style avatar for user Davin V Jones
      No, it doesn't violate the 1st law because they are converting mass into energy via fusion.

      Gravity is a property of all mass. The more massive an object, the more gravity it exerts.

      Not all knowledge is passed from generation to generation. Many species don't pass any knowledge, let alone do they even have a nervous systems capable of building or containing knowledge. Plants and bacteria are two large sets that don't contain knowledge.
      (6 votes)
  • duskpin ultimate style avatar for user demhat
    might artificial intelligence be a threshold?
    I mean maybe in the future, artificial intelligence was be going to be improved enough to help us answer some questions we can't answer or understand without its help. I don't mention AI which destroys humanity or takes control

    (I hope you get the point what I exactly mean)
    (4 votes)
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  • aqualine tree style avatar for user dresdenrobson
    Nice-John Green
    (2 votes)
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  • blobby green style avatar for user seasonkelsey
    humans did not evolve from monkeys? what do you think?
    idea: if humans evolved from monkeys then why do we still have monkeys? wouldn't they all be humans now? and its like the gerbil and the hamster thing. just because a a hamster is similar to a gerbil does not mean that the hamster evolved from a gerbil yes they come from the same family of genes like how humans have similar genes to apes but that doesn't mean that one came from the other
    (0 votes)
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    • duskpin ultimate style avatar for user Aria
      Edit: sorry uh that got a bit long huh lol.
      In summary: sometimes a single species don't or can't reproduce with each other, and gets separated into 2 or more different gene pools, they continue to co-exist without reproducing together, thanks to random mutations they eventually get genetically sealed off from each other permanently and can't create viable offspring together anymore. That's what creates new species and it's a gradual process that takes 100,000s to millions of years to happen for slow-reproduction species like primates.
      Read on if you want more details :)


      Humans did not evolve from monkeys, we are apes. Monkeys and apes are both primates but different families, one obvious difference is that apes, unlike monkeys, are tail-less (think chimps, gorillas, and humans).

      Also other apes that exist today are "sister" species to us, we did not evolve from them nor did they evolve from us, we both evolved from a now-extinct common ancestor (it's not extinct because it died, but because it became us and all the other apes, including the apes the did die off). If you go even far back in time you will find the also now-extinct common ancestor of apes and monkeys.

      So why do we still have other non-human primates? To answer that you have to understand how a new species forms: it takes 100,000 to millions of years, during this time random mutations are happening all the time and changing the species just a tiny bit with every new born baby, the mutations are what drives evolution, slowly but surely.

      So why aren't we all the same exact species? Because we don't and can't all reproduce with everyone else, there are various reasons why that ends up happening, sometimes a part of a spices breaks off and migrates elsewhere, and those same mutations that are happening all the time ends up changing what once was the same exact species into two separate and genetically different ones that can't reproduce and have successful offspring anymore, so they're cut off from each other permanently.

      Bonus: one interesting thing that isn't talked about much, is how it was possible that the humans that left Africa would eventually become an entirely different species from the people in Africa given enough time (think in another 300,000 years..? or probably even more), that of course won't happen now because people from all over the world mate with each other and have been doing so for 1000s of years.

      However genetic studies show that people from true African descent have a much higher genetic diversity than anyone else in the world (because Africa is where all humans originated, those that wandered outside had a smaller gene pool because there weren't many of them), the only reason we don't have "Africa-humans" and "non-Africa-humans" species is because we continued to marry each other and never truly separated, and also because only about 70,000 have passed since groups of humans left Africa, which is not that much seeing as we reproduce relatively slowly.

      This is also how new exotic breeds of cats and dogs are made, they reproduce much faster than humans, so new breeds rise up in much less time. But even then, I believe all breeds of dog can still interbreed successfully, because not enough time has passed and not enough separation for them to become entirely separate species.
      (6 votes)
  • leafers sapling style avatar for user nevaehnewton
    Humans did not evolve from monkey because if they did how do we still have monkeys and where do the monkey we have now come from
    (0 votes)
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