You may easily understand how this should be so. Man, at first, from what we are able to learn about him, knew very little of farming. Such ideas as a "rotation of crops," or of manuring the fields were probably quite unknown to him for very many ages. The first men whom we are able to learn anything about seem to have depended on the hunting of other animals for their living. Then came a time when they began to live on their flocks and herds. Now, both for the hunting and for the living by keeping cattle and sheep, they had to be constantly on the move. They would kill out all the game in one district and therefore have to move on to another. Or their cows and sheep would eat up all the pasture in one place and so they had to be moved to fresh feeding-grounds. These two first stages, which all the scholars recognise, in man's story require that the people who lived in them should be always moving, or at least ready to move. The stages are called the Hunting Age and the Pastoral Age respectively. The next age is called the Agricultural Age, when man began to give "culture" to the "ager," or field. He was able to settle then. It was not necessary for him to be constantly on the move when he had begun to live by the crops which he grew. But he was not yet a very clever or scientific farmer. He could grow good crops only when Nature helped him very freely, only {5} on the best soils, only in the river valleys or lands watered by the rivers, and in a favourable climate. The soil of Mesopotamia is still considered the most t naturally rich in all the world: the Nile overflows its banks every year, and the overflow leaves a wonderfully rich mud behind it; the climate both in Mesopotamia and in Egypt is very favourable to the growth of vegetation. Therefore, it is not to be wondered at that when men began to lead a settled life they settled themselves down along the courses of these two great rivers--I write two, because I am regarding the Euphrates and Tigris as one, for the moment--and here formed themselves into communities and nations so many in number and so prosperous that they became stronger than any of their neighbours. [Sidenote: Earliest man] And now you are very likely to ask me, "What do we know about the early history of man on the earth, and how do we know it?"