PEOPLE SHARE a common origin with the hundreds of thousands of stars shown here at the center of the Milky Way galaxy. The stars are made visible by infrared imagery from NASA’s Spitzer Space Telescope.
As of Saturday, May 11, 2013
All life on Earth shares a common ancestor. You just have to trace the evolutionary tree over 3 billion years into the past to find it. And while family resemblances get harder to see the further back you go, modern science unmistakably ties us all together.
This is a core principle of modern biology, backed up by every branch of science that touches on life or its processes. Although the fossil record strongly supports evolution, it’s hardly necessary given today’s advanced technologies unimaginable in Darwin’s time.
From man to microorganisms, shared genes and biochemical pathways can be tracked back along the tree of life. We share over 98 percent of our genes with chimpanzees, 90 percent with mice, 40 percent with fruit flies, 15 percent with plants and 7 percent with the lowly but highly successful bacteria. DNA sequences between genes differ more between species, but also reveal the pace and course of evolution.
I’m not Gaian, worshipping the planet as one harmonious organism, but have always found the interconnected nature of life on this planet to be awe-inspiring concept. Yet it turns out even this grand idea is too limited, because our common connections go far beyond just life on Earth.
Listening to Neil deGrasse Tyson, the astrophysicist, first introduced me to the larger picture, and it was just reinforced by reading Neil Shubin’s new book “The Universe Within: Discovering the Common History of Rocks, Planets and People.”
We obviously don’t share genes with rocks or planets. But the atoms that make up our genes, our bodies, the planet and the universe do share a common origin. And just like with our common biologic ancestor, we have to go back to the beginning to find this source.
As the expanding universe began cooling after the Big Bang some 13.7 billion years ago, the first simple atoms of hydrogen and helium formed from the plasma. Over time, gravity drew them together and they coalesced until the pressure and temperatures became so great nuclear fusion was triggered. The first stars had begun to shine.
Just as happens inside our sun today, nuclear fusion combined the light elements into heavier ones, creating ever increasing amounts of carbon, oxygen and nitrogen along with other new elements. When these early supermassive stars ultimately collapsed and exploded, they scattered their atoms into surrounding space to be recycled into new galaxies, stars and planets.
Hydrogen, oxygen, carbon and nitrogen are among the most common elements in the universe, and the foundation of all life as we know it. These four atoms make up 96 percent of our bodies, together building the proteins, fats and carbohydrates that define us.
And now combinations of these same atoms, forming simple molecules that are the precursors of proteins and nucleic acids (DNA), have been identified in deep space and on asteroids. They represent the early building blocks of life, and appear to spontaneously come together even under the harshest of conditions.
In short, the universe created the first atoms that made the stars, the stars the atoms that made the planet, and once on the planet the same atoms combined to form us and every other living thing. Our bodies are made of atoms traceable back to the Big Bang and the very beginnings of time.
We may live on a small planet, circling an ordinary star near the edge of a galaxy far from the center of the universe. But we still have something in common with everything else out there. To quote Neil deGrasse Tyson, “We are not figuratively, but literally stardust.”
Lifelong Oregonian Fred Schubert, a The Dalles biologist, has a lifelong interest in general science and science writing. Feel free to submit any comments on this article or suggestions for new topics to fcscience @qnect.net.