The planet Earth is 4.600 million years old. It is difficult for us to think about such an enormous' length of time because it has little meaning for us. We can, however, simplify the idea to make it more understandable. We can compare the planet Earth to a person of forty-six years of age.
Nothing is known about the first seven years of this person's life. Very little information exists about the middle period either. It was only at the age of forty-two that the Earth began to flower.
Dinosaurs and great reptiles did not appear until one year ago. When the planet was forty-five. Mammals only arrived eight months ago. In the middle of last week, man-like apes became ape-like men and began to communicate with each other. Last weekend, the Ice Age covered the Earth.
