Ancient paintings on rock walls feature human figures and animals of today’s rainforest, like deer, tapirs, and jaguars. But they also appear to show animals that went extinct thousands of years ago.

Along the river Gambia in Senegal, there are more than a thousand stone circles. The people who placed these stones would have observed how the locations of sunrise and sunset varied over the year. By aligning the stones to these points, they would’ve been able to track the seasons.