prehistory

Polished axe-head, dating from about 1800 BC (Devizes Museum, Wiltshire, England). The Neolithic period is characterized by the advent of ground and polished axes and adze heads. Polishing the stone tool by grinding a fine abrasive against it gave the axe a smoother cutting edge and greater strength. Polished axes were often made of stones such as schist and jadeite, which are harder materials than flint.

A Neanderthal tomb burial from La Chapelle aux Saints, France, dating from about 50,000 years ago (Anthropological Institute, Turin, Italy). The extreme infirmities of the skeleton of an old man found at La Chapelle suggest that he was cared for by other members of his clan, or he would not have survived as long as he did. Such discoveries helped to change the original perception of Neanderthals as being brutish and ape-like.

Human cultures before the use of writing. The study of prehistory is mainly dependent on archaeology. General chronological dividing lines between prehistoric eras, or history and prehistory, are difficult to determine because communities have developed at differing rates. The Three Age System of classification (published in 1836 by the Danish archaeologist Christian Thomsen) is based on the predominant materials used by early humans for tools and weapons: Stone Age, Bronze Age, and Iron Age.

Human prehistory begins with the emergence of early modern hominids (see human species, origins of). Homo habilis, the first tool user, was in evidence around 2 million years ago, and found at such sites as Koobi Fora, Kenya and Olduvai Gorge, Tanzania.

Stone Age

Old Stone Age (Palaeolithic) 3,500,000–8500 BC. Stone and bone tools were chipped into shape by early humans or hominids from Africa, Asia, the Middle East, and Europe, as well as later Neanderthal and Cro-Magnon people; the only domesticated animals were dogs. Some Asians crossed the Bering land bridge to inhabit the Americas. Prehistoric art was being produced 20,000 years ago in many parts of the world; for example, at Altamira in Spain, Lascaux in France, in southern Africa, and in Australia.

Middle Stone Age (Mesolithic) and New Stone Age (Neolithic). Bone tools and stone or flint implements were used. In Neolithic times, agriculture and the domestication of goats, sheep, and cattle began. Stone Age cultures survived in the Americas, Asia, Africa, Oceania, and Australia until the 19th and 20th centuries.

Bronze Age

Iron Age

Study of the remains of early humans covers age, material, function, and social and physical environment. It considers the quest for food and dwelling, conditions of commerce, trade, labour, and communications, the state of peace or war, and spiritual belief, including the disposal of the dead. Discovery and analysis of remains through archaeology is the first step, followed by interpretation of results. Knowledge of prehistory has been greatly advanced by the increase in data resulting from improved excavation, analysis, absolute dating, and relative dating techniques. But prehistory is increasingly an area of new ideas based on interpretation of landscape and extant social behaviour, drawing on other fields such as cognitive science, anthropology, and economics, including critiques based on neo-Marxist and feminist theories, together with environmental science, and, in the analysis of early modern human behaviour, primatology and animal behaviour.

Relative dating Relative chronology does not determine the period of calendar time indicated by a layer or prove that a period in one area is contemporary with that of another. Stratigraphy establishes a relative chronology in stratified deposits such as those left by the successive undisturbed layers of human occupation in a cave or a dwelling site, where the lowest layer will yield the oldest remains. Cross-dating is sometimes possible with ancient literate civilizations such as those of Babylonia, Egypt, and Crete, but this cannot be applied before about 3100 BC.

Typology, the grouping of artefacts into types with shared attributes, is allied to the relative dating method seriation, in which artefacts are placed in chronological sequence according to their progressive evolution or degeneration in technology and style. The distribution of the Beaker people, who spread out over Europe from the 3rd millennium BC, and the successive waves of the early English Neolithic Windmill Hill culture, found also in Switzerland and France, have been determined through the typology and seriation of their pottery.

Absolute dating Absolute dating determines age in calendar years by reference to a fixed timescale and may be established using scientific techniques such as radiocarbon dating, potassium-argon dating, electron spin resonance, fission-track dating, and archaeomagnetic dating.

Climatic change Dramatic changes in climate have taken place over a considerable part of the Earth's surface throughout prehistory with significant effects on flora. Studies focusing on these changes include dendrochronology, which provides an absolute chronological system based on tree-ring growth, and pollen analysis, used in relative dating and in palaeoenvironmental and palaeoclimatic reconstruction. Pollens found in the peat bogs of Britain and Scandinavia, in the Alps and other parts of central Europe, reflect the history of forest and vegetation in the Holocene epoch (post-Ice Age and most recent epoch). There are three main phases in this period, known in one terminology as Pre-Boreal, Boreal, and Atlantic, and in others by a system of numbers. Pollen analysis has enabled layers of peat bog to be accurately divided into intervals of a century. In Britain it has yielded excellent results in the Cambridge fens.

Geochronology Geochronology is the science of measuring geological time. In the Pleistocene geological period, a timescale is provided by the glacial and interglacial periods and by pluvials, periods of heavy rain that fell in regions now dry, such as modern Zambia and Zimbabwe, and Iran. By 1940, the Swedish geologist Gerard de Geer had dated the 3,600-year glacial retreat in southern Scandinavia using varve analysis (study of annually formed glacial deposits).