One of the greatest riddles of the universe is the existence and emergence of life. How could something living arise from something non-living? Where is the line between chemistry and biology—between the non-living and the living? Perhaps there is no clear line. And what is “life” in the first place? The question of abiogenesis is one of the biggest challenges for modern astrobiology. How did the first self-replicating molecules form? What physical and chemical conditions are needed for life to emerge from non-living matter? And how did evolution begin, leading to ever greater complexity?
The origin of life is not only a scientific question. It is also an existential one—a challenge to how we understand the world, a historical and philosophical problem. Humans have always wondered about the origin of life and our own birth. We see it in creation myths across religions and in ancient epics from the Epic of Gilgamesh to Hesiod’s Theogony.
Over the centuries, philosophers and scientists have tackled the question from different angles, with a wide range of arguments. In the 17th and 18th centuries, naturalists observed that insects, worms and other small organisms seemed to arise spontaneously from dead matter. In the 19th century the hypothesis of panspermia—the idea that life reached Earth from elsewhere, “packaged” in meteorites—became one possible answer to how life appeared on our planet. But panspermia only moves the problem elsewhere: if life came from somewhere else, how did it arise there and then reach us?
To begin the journey of life we have to answer what a living organism is. According to Darwinian theory, something living can resist the 2nd law of thermodynamics by constantly feeding itself with energy: it feeds, metabolises and can make copies of itself by producing offspring. Something non-living is left to the “chance” of the universe.
Every organism on Earth is related to every other. We are one big family—every creature that has walked, swum or flown on Earth. That is not just a poetic line. It is literally true. Starting from our own family tree and going further and further back, we pass through organisms that differ from us until we reach the first single-celled forms of life. Those organisms are quite literally our ancestors. The pioneers of life.
Going back even further, some four billion years, we reach a fuzzy boundary between the end of chemistry and the beginning of biology. The origin of life is a deep philosophical question about the very nature of life, and thus about our own existence. It raises many questions for the philosophy of science—for example how we classify, understand, develop and justify scientific theories.
Perhaps the most debated philosophical issue in astrobiology is the very definition of “life.” If we are searching for life in space, we need at least some idea of how to tell the living from the non-living. It also shapes ethical guidelines for science: if Earth life or life of another origin could survive in space, we need ways to avoid cross-contamination and flawed scientific conclusions.
To the question of whether there is a line that separates where chemistry ends and biology begins, the answer is both yes and no. We draw such lines for every kind of question—philosophical or not—to make it easier to study the world. If we ask ten people what life means, we get ten different answers. Life might be the physical and mental flow of experiences that make up a person’s existence, or it might be an illusion born of the human brain’s difficulty in grasping certain complex physico-chemical processes. If one day we reach a reasonable answer to the riddle of life’s origin, that discovery will change forever even our own sense of what life is.
For more reflection on existence and how we see the world, read The Violence Within Us and There Is No Destination.
Happy Life Team
