The theory that the early stone workers had a core industry and the later ones worked flakes was rudely upset by the discovery of flaked tools—called Cromerian—in an English stratum as old as the French sources of the first hand axes, and possibly older. Some say they lie at the beginning of the Great Ice Age or at the end of the earlier period, the Pliocene. This demonstration of a very early flake industry was reenforced by the discovery of a special type of flaked tool—the Clactonian—which runs from late Abbevillian into Acheulean times. Another type—the Levalloisian—laps over from the Acheulean into the Mousterian. The core industries and the flake industries simply would not stay nicely separated. The first excavators had found only hand axes because these tools were so much more interesting than scrapers; later students found flake tools in the same ancient levels. No hand axes turned up in Clactonian culture-sites, but they appeared at the end of the Levallois, and the flake-loving Mousterians made them for a time. “Flake and core run parallel to one another in time,” says W. B. Wright, “and even intermix.”[7] [Illustration: PALEOLITHIC TYPES AND INDUSTRIES _A chart of the core-, flake-, and blade-making traditions and industries, devised and dated by Robert J. Braidwood.[8] The dates indicate the approximate beginning and end of the various types of artifacts. Usually the same group of men made different kinds of tools within one industry. The Solutrean was distinguished for double-faced, leaf-shaped projectile points, rather than blades._] [Illustration: MAN’S FIRST PERFECTED TOOL _Three European hand axes that may bridge 300,000 years. They are, top, Pre-Abbevillian; left, Abbevillian; and right, Acheulean. The last is one of the tools found by John Frere at Hoxne in 1715. Most hand axes are not so well formed. Somewhat similar tools have been found in American Indian cultures hafted at the top of a wooden handle or in the middle, as a sort of spokeshave. (After Osborn, 1915; Leakey, 1935; and Burkitt, 1933.)_] If we do not try to apply the core-versus-flake theory too broadly and too strictly, it suggests a fascinating picture of two kinds of men and two kinds of life through the first two-thirds of the Great Ice Age. One kind dominated during the cold of the glaciations; the other, during the warmth of the interglacials. For the flake tools of the Clactonian and Levalloisian peoples are found mainly with the fossils of cold-loving animals in the north and east of Europe, and the core tools of the Abbevillian and Acheulean peoples with warmer-blooded animals in the west and south.