As to culture, the Neolithic period extends in Western Europe from about 2000 to 10,000 B.C.: and to that age is usually attributed the introduction of agriculture, the domestication of animals, pottery, weaving, permanent constructed dwellings, and monuments requiring collective labour; but some of these improvements may be of earlier date. In other parts of the world, _e. g._ in the Eastern Mediterranean region, such culture is probably older, but still comparatively recent. What is known as the Palæolithic stage of culture is often supposed to have begun early in the second quarter of the Pleistocene period, giving us a retrospect of (say) 300,000 years. But if we include under “Palæolithic” all unpolished stone-work that shows clear signs of having been executed according to an idea or mental pattern (and this seems a reasonable definition), the “rostro-carinate” implements must be so called, and then the beginning of this culture must be pushed back into the Pliocene.[55] In Pliocene (and perhaps Miocene) deposits have further been discovered numerous “eoliths”: stones so roughly chipped that they do not imply an idea-pattern; so that, whilst many archæologists accept them as of human workmanship, some experts dispute their claim to be considered artefacts. Of course, there must be eoliths; the only question is whether we have yet unearthed any of them. Our forefathers cannot have begun by shaping stones to a definite figure and special purpose. Beginning with stones taken up as they lay, they discovered that a broken stone with a sharp edge inflicted a worse wound than a whole one; then broke stones to obtain this advantage; used sharp fragments to weight clubs; and very slowly advanced to the manufacture of recognisable axes and spear-heads, meanwhile discovering other uses for flaked stones; and it seems to have needed at least 1,400,000 (or 2,800,000) years to arrive at the poorest of known palæoliths. This strikingly agrees with the law, often stated, that the progress of culture is, by virtue of tradition, cumulative, and flows, as a stone falls, with accelerating velocity: in spite of the ebb, to which from age to age we see it to be liable. At any one time, moreover, the art of stone-working was, probably, even in adjacent tribes, at different stages of advancement; it depends partly upon the kind of stone obtainable; but it has been only recently that such contrasts could occur as Herodotus[56] describes among the hosts of Xerxes: when, beside the well-accoutred Persians and Medes, marched Libyans and Mysians armed with wooden javelins hardened in the fire, and Ethiopians with stone-tipped arrows and spears headed with the sharpened horns of antelopes.