The Sumerians, however, ultimately achieved an intellectual conquest of their conquerors. Although the leaders of invasion may have formed military aristocracies in the cities which they occupied, it was necessary for the great majority of the nomads to engage their activities in new directions after settlement. The Semitic Akkadians, therefore, adopted Sumerian habits of life which were best suited for the needs of the country, and they consequently came under the spell of Sumerian modes of thought. This is shown by the fact that the native speech of ancient Sumer continued long after the dawn of history to be the language of Babylonian religion and culture, like Latin in Europe during the Middle Ages. For centuries the mingling peoples must have been bilingual, as are many of the inhabitants of Ireland, Wales, and the Scottish Highlands in the present age, but ultimately the language of the Semites became the prevailing speech in Sumer and Akkad. This change was the direct result of the conquests and the political supremacy achieved by the northern people. A considerable period elapsed, however, ere this consummation was reached and Ancient Babylonia became completely Semitized. No doubt its brilliant historical civilization owed much of its vigour and stability to the organizing genius of the Semites, but the basis on which it was established had been laid by the ingenious and imaginative Sumerians who first made the desert to blossom like the rose. The culture of Sumer was a product of the Late Stone Age, which should not be regarded as necessarily an age of barbarism. During its vast periods there were great discoveries and great inventions in various parts of Asia, Africa, and Europe. The Neoliths made pottery and bricks; we know that they invented the art of spinning, for spindle-whorls are found even in the Gezer caves to which we have referred, while in Egypt the pre-Dynastic dead were sometimes wrapped in finely woven linen: their deftly chipped flint implements are eloquent of artistic and mechanical skill, and undoubted mathematical ability must be credited to the makers of smoothly polished stone hammers which are so perfectly balanced that they revolve on a centre of gravity. In Egypt and Babylonia the soil was tilled and its fertility increased by irrigation. Wherever man waged a struggle with Nature he made rapid progress, and consequently we find that the earliest great civilizations were rooted in the little fields of the Neolithic farmers. Their mode of life necessitated a knowledge of Nature's laws; they had to take note of the seasons and measure time. So Egypt gave us the Calendar, and Babylonia the system of dividing the week into seven days, and the day into twelve double hours.