Patient evolution's billion-year wait

摘要

Long before evolution on Earth kicked in with a vengeance, it seemed to stall completely. From 1.7 billion years ago, for a billion boring years, Earth remained a slimy, near-static world of algae and microbes. The pace picked up 750 million years ago: glaciers spread, complex animals appeared, and by 520 million years ago the Cambrian revolution- an explosion of varied life - was under way. The reason for that long stasis has been a mystery.