Dating the past

Dating the past has been a central issue in archaeology throughout its development and remains fundamentally important. Chapter 1 described how, between ad 1500 and 1800, the biblical account of the Creation, the Flood and the

peopling of the world had been undermined by European voyages of discovery and the development of geology. By the 1860s Bishop Ussher’s date of 4004 bc for the Creation had been largely forgotten, while Darwin’s theory of evolution by natural selection had extended the geological perception of the Earth’s long, slow development to plants and animals (Van Riper 1993). Enlightenment ideas about social progress were supplemented by Romantic interest in origins and change and, once prehistory had been conceptualised, it was rapidly subdivided into ages dened

by artefact technology and social evolution. However, one major obstacle remained: even if bones and artefacts were carefully excavated from geological or archaeological contexts and recorded in relation to stratication, this only placed them into a relative sequence which had no meaning in terms of absolute time (Chapter 3, p. 100). Absolute dating in calendar years remained rmly in the hands of archaeologists working on historical periods, initially the Classical civilisations of Greece and Rome, and then Egypt and the Near East as their scripts were deciphered in the early nineteenth century. In contrast, archaeological nds from Scandinavia that had been arranged neatly into three successive ages of stone, bronze and iron were completely undatable until Roman imports began to appear alongside them in the Iron Age. By the early twentieth century some progress had been made in cross-dating prehistoric nds from northern and western Europe to Egypt, oen very indirectly. Similar procedures could be carried out in South America, India, China and other parts of the Far East where literate civilisations existed, but elsewhere dating only began with the rst contacts between native peoples and European explorers and colonisers. Some hope of establishing absolute dates without historical documents emerged from environmental sciences in the early twentieth century when scientists began counting annual layers of lake sediments or growth of tree rings from the present into the past. Meanwhile, the new science of nuclear physics began to provide radiometric dates for the age of the Earth and the succession of geological ages. Following the development of radiocarbon dating in the 1940s the rst absolute dates for prehistory began to be measured from samples of charcoal, wood, bone and other organic materials. e radiocarbon revolution has continued for more than y years, gradually extending both the precision and the range of the technique. A growing number of other scientic methods have been developed for dating inorganic materials, and for extending chronology beyond the reach of radiocarbon, which is increasingly imprecise for samples more than 50,000 years

old and virtually unusable by 100,000 years. It is increasingly di¶cult for prehistorians working in the twenty-rst century to conceptualise the problems experienced by their predecessors, and approaches to interpretation before the 1960s are consistently criticised. Culture history and diffusionism may, with hindsight, seem excessively preoccupied with classication and social evolution and to have applied unsophisticated historical interpretations instead of asking fundamental questions about human behaviour (Chapter 6, p. 258). However, their exponents did not have the luxury of a global framework of independent, absolute dates; the di¶culties they faced may be appreciated by looking more closely at typology and cross-dating.