Man first appeared on earth half a million years ago. Then he was little more than an animal; but early man had several big advantages over the animals. He had a large brain, he had an upright body, he had clever hands; and he had in his brain special groups of nerve cells, not present in animals, that enabled him to invent a language and use it to communicate with his fellow men. 46) This ability to speak was of great value because it allowed men to share ideas, and to plan together, so that tasks impossible for a single person could be successfully undertaken by intelligent team-work. Speech also enabled ideas to be passed on from generation to generation so that the stock of human knowledge slowly increased.It was these special advantages that put men far ahead of other living creatures in the struggle for existence. They can use their intelligence against their difficulties and master them.Since these far-off times, when he first appeared, man has achieved a great deal. He has used animals, steam, electricity and oil to move himself more and more quickly from place to place. He has overcome rivers and seas with rafts, canoes, boats and ships of endless variety. 47) He mastered dark ness, to% first with dim lights and later with brighter and brighter lamps, until he can now make for himself so dazzling a light with an arc-lamp that, like the sun, it is too strong for his naked eyes.48) Man found that his own muscles were too weak for the work which he wanted to do; he explored many forms of power—wind, water, steam, electricity—until now he has his hands on the ultimate source of physical energy, the nuclear power which ties together the smallest units from which all matter is made. From man’s earliest days the flight of birds has raised his wonder and desire. Why should he not fly as they did Then he began to experiment. At last he learnt how to make the right machines to carry him through the air. Now he can fly faster than sound. Already he has plans for conquering space, and a series of experiments has been completed. 49) It will not be long now before man takes a giant step away from his planet and visits the moon, learning what it is like to have no weight to his body, no upward direction and no downward.Man, always a wanderer, has to overcome the difficulty of adapting himself to different climates, 50) Fortunately, in spite of having no thick skin or warm fur to protect him, he is peculiarly strong compared with other living creatures, most of whom are unable to live far outside the region that suits them best. Man, however, can go almost everywhere. You will find him living on the plains and up in the hills; he lives in damp areas and in dry; in the forests of the hot regions of the earth, and in snow huts in the Far North. It will not be long now before man takes a giant step away from his planet and visits the moon, learning what it is like to have no weight to his body, no upward direction and no downward.