The material remains of the past can be studied with the help of archaeology. Archaeology is a science that enables to systematically dig the successive layers of old mounds and to form an idea of the material life of the people of the past on the basis of remains found there.
Archaeology is very important to study prehistory i.e. the period before the invention of writing. History is basically based on written material. Although writing was known in India by 2500 BC in the Indus culture, its script has not so far been deciphered.
Thus, though the Harappans knew how to write but the historians have not been able to read it. Their culture is placed in the period called protohistoric phase. The first script to be deciphered was Brahmi which was used in the Ashokan inscriptions and it belongs to the third century BC.
Excavations have brought to light the tools of early humans in India going as back as seven lakh years. The excavated sites belonging to the Harappan period show the layout of the settlements and the form of the houses in which people lived, the type of pottery, tools and implements they used and the kind of cereals they consumed.
In south India some people were buried along with their tools, weapons, pottery and other belongings under big and heavy stones. These graves are known as megaliths. By digging them we learn about the life of people who lived in the Deccan and south India before the third century BC.
The dates of remains found in excavations are fixed by various methods. The most important of them is the Radiocarbon or Carbon 14 (C14) dating method. Carbon 14 is a radioactive carbon present in all living objects. It decays, like all radioactive substances, at a uniform rate when the object is dead. By measuring the loss of C14 content in an ancient object (wood or bone) its age can be determined.
The history of climate and vegetation is known through an examination of plant residues, and especially through pollen analysis. On this basis it is suggested that agricuture was practised in Kashmir and Rajasthan around 7000 - 6000 BC.
The nature and components of metal artefacts can also be analysed scientifically, and consequently the mines from which metals were obtained are located and stages in the development of metal technology identified. The geological studies provide an idea of the history of soil, rocks etc, where prehistoric man lived. Human history cannot be understood without an idea of the continuing interaction between soils, plants and animal, on one hand, and humans, on the other. Taken together with archaeological remains, geological and biological studies act as important sources for the reconstruction and development of human history.