Role of physical and chemical sciences in archaeology
Physical sciences (Physics and Chemistry) also play a very important role in the reconstruction of past human societies from the archaeological record.
Earlier archaeological sites and their deposits were dated in relative terms with the help of methods like stratigraphy, stylistics of artifacts and monuments, and degree of patination. During the last half a century a number of absolute dating techniques developed in Physics and Chemistry have proved to be very useful for dating archaeological sites. Their time range has now been extended to nearly three million years. Radiocarbon, archaeomagnetism, potassium-argon, uraniumthorium, fission-track, electron spin resonance, and thermoluminescence are some of these methods.
The carbon 14 (radiocarbon-carbon of atomic weight 14) method gives absolute date up to ca. 50,000 B.P. on wood, wood charcoal from fire, peat, grass, cloth, shell, bones, dung, remains of plant and animal life. This dating technique was for the first time introduced in 1949 by Williard F. Libby. Similarly, potassiumargon method gives dates ranging up to a few million years on rocks, minerals, pottery, volcanic glasses and meteorites etc. and the thermoluminescence (TL) give dates on rocks, minerals and pottery.
In India too, these and other dating methods have now begun to be used commonly for dating archaeological materials and sediments. C-14 dates have pushed the antiquity of the Indus civilization to the beginning of the third millennium B.C. and the beginning of crop and animal husbandry to 6th-7th millennium B.C. Likewise, the Stone Age sites of Riwat and Uttarbaini in the Siwalik zone have been dated to beyond two million years by palaeomagnetism. The Acheulian sites of Isampur and Attirampakkam in South India are dated to 1.2 and 1.5 million years by electron spin resonance and cosmogenic nuclide methods, respectively. Indeed we realise that these dating methods taken from physical sciences have caused a revolution in archaeological chronology in India.
Techniques borrowed from organic and inorganic chemistry have also contributed in a significant way towards the analysis and interpretation of archaeological materials. The application of these techniques has, for example, given fresh knowledge about ancient copper, iron and glass technology. Also, analyses of food and blood residues on ancient objects and pottery containers led to interesting information about preparation of food items and their consumption. For example, chemical analysis of starch grains on stone tools shows that already in Middle Palaeolithic times sun-dried bread of wild grass seeds was being prepared and consumed in Africa and Europe.