What Was It Like When Life Began On Earth?
“At some point on our planet, in the very early stages, the molecules that are abundant and precursors to life, under the right energy and chemical conditions, began to simultaneously metabolize energy, respond to the environment, grow, adapt, evolve, and reproduce. Even if it would be unrecognizable to us today, that marks the origin of life. In a radically unbroken string of biological success, our planet has been a living world ever since.
While Venus and Mars may have had similar chances, radical changes to Venus’ atmosphere rendered it a searing hothouse world after just 200-300 million years, while the death of the Martian magnetic field caused its atmosphere to be stripped away, rendering it solid and frozen. While asteroid strikes may send Earth-based life off-world, throughout the Solar System and galaxy, all the evidence suggests that we are where it started.
By 9.4 billion years after the Big Bang, Earth was teeming with life. We’ve never looked back.”
When most of us learned about the history of life on Earth in school, all we had were ideas and theories about how it might have gotten started. As you may have guessed, science progresses quickly, and we now have extraordinary evidence for an ancient universal common ancestor, for life existing just a few hundred million years (at the latest) after Earth’s formation, and for life beginning on Earth itself, not before. We even have candidate locations for where!