The first two stages in the development of civilized man were probably the i

The first two stages in the development of civilized man were probably the invention of primitive weapons and the discovery of fire, although nobody knows exactly when people acquired the use of the latter.
    The origin of language is also obscure. No doubt it began very gradually. Animals have a few cries that serve as signals, but even the highest apes have not been found able to pronounce words even with the most intensive professional instruction. The superior brain of man is apparently necessities for the mastering of speech. When man became sufficiently intelligent, we must suppose that he gradually increased the number of cries for different purposes. It was a great day when he discovered that speed could be used for narrative. There are those who think that in this respect picture language preceded oral language. A man could draw a picture on the wall of his cave to show in which direction he had gone, or what prey he hoped to catch. Probably picture language and oral language developed side by side. I am inclined to think that language has been the most important single factor in the development of man.
    Two important stages came not too long before the dawn of written history. The first was the domestication of animals; the second was agriculture. Agriculture was a stage in human progress to which subsequently there was nothing comparable until our own machine age. Agriculture made possible an immense increase in the number of the human species in the regions where it could be successfully practiced. They were, at first, only those in which nature fertilized the soil after each harvest.