People Arrive on the Scene

Millions of plants and animals have lived on the Earth in all its millions of years of history. But only one single species has ever arisen to the position of being the completely dominant animal, and that is the human species. Before the coming of humans, it was groups of species, such as the dinosaurs, which were dominant.

Stages in the evolution of the human species

Our earliest ancestors

Some of our earliest ancestors were the group of small insect-eating mammals such as megazostrodon mentioned on the 'Early Mammals' page. The primates which were to become the direct ancestors of humans appeared about 36 million years ago. The early primates took to the trees for food and protection. In order to jump from one branch to another, it was a big advantage for both eyes to be able to focus accurately on the same spot.

Binocular vision

Gradually, over a period of several million years, the eyes of these early primates moved from the side of the head towards the front, giving what is called binocular vision. This helped them to see objects more accurately.

The improvement of sight made the sense of smell less important. Long noses or snouts were not needed any more, and the animals' faces became flatter. With binocular vision came improved muscle co-ordination and a better sense of balance. Claws on the fingers and toes were replaced by flat nails. To improve the ability to grasp branches, the thumbs developed so that they could be bent in front of the other fingers on the hands. In time this adaptation allowed humans to grasp and handle objects such as food, tools, ploughs, weapons and, eventually, pens.

Down from the trees

Some time between the end of the Miocene and the beginning of the Pliocene period, some of the primates came down from the trees and took up life on the open grassy plains of Africa, Asia and Western Europe. One type which lived in East Africa and India was showing signs of the human-primate to come. This animal ran about on its hind limbs, leaving its fore limbs free. Although its teeth were almost useless as weapons, it used its grasping hands to lift and use sticks and stones for defence and for catching prey.