About 600 million years ago, life on Earth was pretty much just a homogeneous bunch of simple, soft-bodied species. But in an evolutionary blink of an eye, that all changed. A longstanding geological mystery could explain why our distant ancestors suddenly developed skeletons.
In less than a hundred million years, life on Earth shifted away from these simple organisms to creatures with shells and bones. The emergence of the first skeletons helped drive the massive increase in biodiversity and the emergence of much more complex multicellular life. This great shift is known as the Cambrian Explosion, and it’s arguably the most dramatic biological event since the first emergence of life itself.
Unfortunately, the geological record tends to obscure what really happened during the Cambrian Explosion… or so we thought. There’s a bizarre discontinuity between the sedimentary rocks of the Cambrian and the much more ancient igneous and metamorphic rocks that lie beneath them. It’s as though millions of years worth of rock formations just up and vanished from the geological record, leaving behind a stark boundary between the ancient and more recent rocks.