Life’s first major catastrophe crept across the planet with the spread of ice. Early life had been thriving in a warm greenhouse world, as creatures such as trilobites, corals, brachiopods and more evolved to fill in the coastal shallows. But around 445 million years ago, for reasons still not fully understood, Earth’s climate tumbled into a frigid state.
Vast glaciers locked seawater into ice and drained the life-filled shallows so many species inhabited, leading many of them to go extinct. When the climate again shifted and warmed over the next million years, the stricken habitats were inundated by seawater once more, and the rapid change caused species that had survived the first change to again come under pressure. The one two-punch would lead 85 percent of marine species to disappear—and come to be known to paleontologists as our world’s first mass extinction.
Extinction is a fact of life. Of all the species that have ever evolved on our planet, the overwhelming majority no longer exist. Even as life continues to evolve and respond to Earth’s ever-changing conditions, every species we perceive will eventually perish.
Some will leave descendent species as part of life’s billions-year-old story, others will be the last of their lineage, but all will eventually meet the same fate. And against this steady background of evolution and extinction, there have been multiple periods when species vanished faster than new species appeared. “To understand the history of.