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The dispersal of early humans from Africa by 1.75 Myr ago led to a marked expansion of their range, from the island of Flores in the east to the Iberian peninsula in the west. This range encompassed tropical forest, savannah and Mediterranean habitats, but has hitherto not been demonstrated beyond 45 degrees N. Until recently, early colonization in Europe was thought to be confined to the area south of the Pyrenees and Alps. However, evidence from Pakefield (Suffolk, UK) at approximately 0.7 Myr indicated that humans occupied northern European latitudes when a Mediterranean-type climate prevailed. This provided the basis for an 'ebb and flow' model, where human populations were thought to survive in southern refugia during cold stages, only expanding northwards during fully temperate climates. Here we present new evidence from Happisburgh (Norfolk, UK) demonstrating that Early Pleistocene hominins were present in northern Europe >0.78 Myr ago when they were able to survive at the southern edge of the boreal zone. This has significant implications for our understanding of early human behaviour, adaptation and survival, as well as the tempo and mode of colonization after their first dispersal out of Africa.
A volumetric method in which the stomach contents are squashed to a uniform depth and the volume is derived from the area of the squash has been evaluated. The apparatus is simple in constiuction and the method applicable to a wide range of fish sizes. The overall error of the method may be as low as 3-5 "/, for well macerated material, though for hard bodied food animals thc coefficient of variation may be up to 8%. These volumetric determinations are not directly proportional to gravimetric measurements but logarithmic conversion curves are readily derived.
I. INTRODUCTIONNumerical and occurrence methods of expressing the composition of the diet of fishes are the most rapid in use but have the major disadvantage of over-emphasizing the importance of numerous small items and cannot deal effectively with plant material or indeterminate numbers of fragmented, yet identifiable, animals. Volumetric or gravimetric methods, however, have the opposite bias and over-estimate the importance of larger, yet less frequently eaten, food items. Windell (1968) suggested a combination of volumetric and numerical methods to indicate the importance of food items. In the absence of data on the relative rates of digestion of different food items of various sizes this combination is probably a reasonable compromise.
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