Scientists have pieced together enough clues to Earth’s past climate to graph the average temperature from 485 million years ago to the present — back to a time long before dinosaurs and even trees, when the land was either barren or hosted mostly moss, millipedes and primitive insects. This new work shows temperatures spent hundreds of millions of years bouncing up and down, from climates similar to ours to ones that were steamier by about 15C (30F).

Earlier attempts to chart our planet’s ancient climate suggested vastly hotter average temperatures — 30C (60F) above today’s — that gradually cooled. The new analysis, published this week in Science, instead shows a series of extreme oscillations but no overall trend.