How could an asteroid kill the dinosaurs?
About 65 million years ago, a massive asteroid hit Mexico. It caused an enormous explosion and threw up millions of tonnes of debris into the atmosphere. This blocked out the sun for many years which cooled the earth and killed most of the vegetation. The dinosaurs could not survive in these conditions. Some plants, insects and a small group of tiny mouse-like animals called mammals survived and they now populate the planet. Humans are evolved from these first mammals.
