Fossilized skeletons and shells clearly show how evolution and extinction unfolded over the past half a billion years, but a new analysis extends the chart of life to nearly 2 billion years ago. The chart shows the relative ups and downs in species counts, telling scientists about the origin, diversification, and extinction of ancient life. With this new study, the chart of life now includes life forms from the Proterozoic Eon, 2,500 million to 539 million years ago. Proterozoic life was generally smaller and squishier -- like sea sponges that didn't develop mineral skeletons -- and left fewer traces to fossilize in the first place.
