Undeniable by Bill Nye Read Free Book Online

suffocated along your route, because there was no significant amount of oxygen in the air. Earth’s oxygen was a byproduct of photosynthesis in those early microbes. The blue-green bacteria, along with you and me, are the only single species known to be capable of altering the climate of an entire planet.
    Two months into your trek, perhaps not too far from Little Rock, Arkansas, the ancient supercontinent of Rodinia has formed. Another month on the road, and you may notice that a more recent ancient supercontinent, Pangaea, has formed. Not all, but almost all of the living things you encounter are in the ocean. Wait, you wouldn’t encounter them, unless you were walking when most of the current interior of the United States was under water, under an ancient inland sea. As you slog forward, unusual and by our standards bizarre sea creatures abound.
    When you’re only 230 kilometers (120 miles) from the eastern shore, you finally come upon the ancient dinosaurs. They are latecomers in the long history of life. You walk in their midst for 100 kilometers. That would be two or three days at a good pace. Along the way, plants that produce flowers appear. Sex is everywhere now.
    Just two kilometers to go now, and the Atlantic Ocean might be in view. And here, you meet the first of us—early versions of humans, living just 2 million years ago. Keep on; you might meet some of our cave-dwelling ancestors. Within five meters of the water’s edge, the ancient pyramids appear. Now, within twenty centimeters, not even the distance from your pinky fingertip to the end of your thumb, the United States as a nation comes to be. The human landing on the Moon is just two centimeters, less than an inch, from the water. Press your toes forward and you arrive at today.
    Now turn around. Look back across the vastness of the continent. Most of it looked barren or desolate on your trek. All that we know of history, all the people and their affairs, everything you’ve come to know, takes place in less than your last stride. It’s this vastness of time that has enabled life to begin and evolution to direct the creation of all the living things we’ve ever known.
    Notice that during about three quarters of your hike, living things were just revving up. There were bacteria, lots of them. But the plants that you and I eat, along with the animals we raise for food and fertilizer, all came to be when you had almost completed your journey. Most of life’s time here on Earth has been spent making the slow evolution from a few crudely self-copying chemicals to the first true cells to relatively uncomplicated, but nevertheless remarkable, living things. It is only very recently in the deep timescale of things that complicated animals like you, me, and my bewitching old girlfriend came to be.
    When Charles Darwin and Alfred Wallace were pondering the consequences of their discoveries, they were deeply troubled by what seemed to be the tremendous amount of time required to get life to where it is now, or where it was when they lived. Darwin published On the Origin of Species in 1859. Radioactivity wasn’t even discovered until 1896, and wasn’t well understood until many years after that. So even as Darwin developed his elegant theory, which he established through dozens of remarkable, diligently executed clever experiments, he was constrained by a lack of a reasonable explanation for how evolution could have enough time to act. He couldn’t explain how Earth could be so fantastically old.
    Darwin’s contemporaries challenged him, even ridiculed him, for asserting that all the living things we’ve ever seen on Earth have a common ancestor and came into existence over this vast expanse of time. How could it be? How could that much time have passed? It is still unimaginable for most of us, let alone to people in Darwin’s day.
    Through the late-nineteenth century, William Thompson (who was Irish but went by