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Directions: Answer the given question based on the following passage:
In the countless ages of the world’s story which preceded the dawn of history, the evolution of life, both animal and vegetable, was profoundly affected by tremendous changes of temperature, whose full significance has only been realized within comparatively recent times. There were cold periods, four in all, known as Ice Ages, which were fatal to many forms of life; these were always preceded or succeeded by Sun Ages, when living things evolved and developed, first great writhing monsters who lived on banks of slime and fought and devoured each other, and who appear to have been destroyed by the intense cold of the Second Ice Age; then mammals such as horses and bears, very small at first, but gradually increasing in size as they became accustomed to their surroundings. The Ice Ages, which were not universal, either killed warmth-loving animals or caused them to migrate to sunnier climes, and it was the last Ice Age which appears to have caused the disappearance from England of such creatures as the elephant, the rhinoceros, and the hippopotamus. During this time the struggle for existence was hard and rigorous, and it gave man the opportunity of developing the brain which has enabled him to assert his mastery over all other created things.
How man originated is still very doubtful. Possibly he is descended from some man-like ape, or it may be that he and the great anthropoid apes such as the chimpanzee, the gorilla, and the orang-outang are all descended from a common ancestor. The earliest evidences of the existence of creatures which may have been human are flints and stones roughly chipped and shaped so that they could be held in the hand and used probably as axes. At Trinal in Java, at Heidelberg in Germany, and in Central Africa remains have been found, such as the top of a skull, teeth and a thigh bone, and a jaw bone, which may have belonged to ancestors of man. The Heidelberg remains probably belong to the warm period before the Fourth Ice Age; those found in Rhodesia and Tanganyika are thought to be much older. With the former were also found remains of rhinoceroses, elephants, lions, and other warmth-loving animals, evidently from a time of great forests and moist climates. Gradually, however, there was a cooling of the temperature and then some great disturbance in Southern Europe, resulting in the separation of Africa and Europe, and so it was no longer possible for animals to wander as they pleased from Europe to Africa or for the hunters to follow them; consequently the men and animals of the two continents would tend to become differentiated. In the gravel and sand-beds of rivers Marne and Somme in France many of the rough flint implements used by these early hunters have been discovered. At Chelles-sur-Marne so many tools have been found that any resembling them are called Chellean. Here there was probably a flint industry; there was another at St. Acheul on the Somme, near Amiens, where much better tools were made. The stone axes of the Acheulean workers (who have given their name to the cool period which followed the warm Chellean period) had more even edges, and flint knives and awls and a primitive hammer were also made. It is probable that they bartered their wares for the fruits of the chase, and so were spared the necessity of hunting for their food.