The origin of life on Earth stands as one of the great mysteries of science. Various answers have been proposed, all of which remain unverified. To find out if we are alone in the galaxy, we will need ...

weather, volcanic eruptions and even animal behavior. Every week, we take a bird's eye view of Earth, and see how it affects the people living on it.

In this feature, explore the history of life on Earth as we know it today, from the earliest bacteria to the first modern humans. To launch the interactive, click on the image at left.— ...

Using fossils as guides, they began to piece together a crude history of Earth, but it was an imperfect history. After all, the ever-changing Earth rarely left a complete geological record.