The Cambrian explosion is a critical moment for life on Earth—and it may have been all about poopSome 540 million years ago, life on Earth suddenly got interesting. Called the Cambrian explosion, scientists have no idea why it happened. The research began as an effort to categorize known examples of fossilized poop, or coprolites, from both before and during the Cambrian explosion. This is harder than you might think: Fossil poop is generally not what paleontologists are looking for on a dig. The correlation reminded the scientists about how modern deep-sea life relies on falling poop to bring vital nutrients down from richer ecosystems above.