The history of ancient India is reconstructed through a wide variety of historical tools and sources. Unlike modern periods, ancient Indian history does not depend mainly on continuous written records. Historians have therefore used archaeological remains, literary texts, inscriptions, coins, monuments, art, foreign accounts, and scientific methods to understand the political, economic, social, religious, and cultural development of ancient Indian society. These sources are particularly important for studying the evolution of social structures in India because they provide evidence about institutions such as family, caste, tribe, village communities, social classes, occupations, gender relations, religion, and patterns of settlement. Archaeological sources are among the most important tools for writing the history of ancient India. Archaeology studies material remains left behind by past societies. Excavations at sites such as Harappa, Mohenjo-daro, Lothal, Kalibangan, Dholavira, Taxila, and many early historic settlements have provided information about settlement patterns, town planning, houses, crafts, agriculture, trade, technology, and social differentiation. The Indus Valley Civilization, for example, is known largely through archaeological evidence because its script has not yet been conclusively deciphered. Differences in the size and structure of houses, craft specialization, public buildings, storage facilities, and burial practices help historians understand the organization and hierarchy of society. Pottery is another important archaeological tool. Changes in pottery styles and technologies help establish chronological sequences and cultural connections. Painted Grey Ware, Northern Black Polished Ware, Black-and-Red Ware, and other pottery traditions have helped historians trace the expansion of settlements and changing economic conditions. The spread of iron technology, agricultural tools, weapons, beads, ornaments, and other artefacts also provides evidence regarding technological change, occupational specialization, trade, and social development. Inscriptions are another major source for ancient Indian history. Inscriptions are writings engraved on rocks, pillars, caves, temples, stupas, copper plates, and other durable materials. The inscriptions of Ashoka are particularly valuable for understanding the Mauryan Empire, administration, religious policy, ethical ideas, and social concerns. Later inscriptions, such as those of the Satavahanas, Guptas, Pallavas, Cholas, and other ruling houses, provide information about political authority, land grants, taxation, religious institutions, social groups, and economic activities. Land-grant inscriptions are especially useful for understanding the growth of agrarian societies and the changing relationship between rulers, landowners, peasants, Brahmanas, and religious institutions. Coins constitute an important source for reconstructing ancient Indian history. Punch-marked coins, Indo-Greek coins, Kushana coins, Gupta coins, and coins issued by various regional rulers provide evidence about political authority, trade, economic activity, religious beliefs, and artistic traditions. The symbols, portraits, legends, metals, weights, and designs on coins help establish chronology and identify rulers. Coins also indicate the circulation of money and the development of commercial networks. Gold coins of the Gupta period, for example, reveal aspects of royal ideology, economic prosperity, military power, and religious practices. Literary sources are equally significant. Ancient Indian literature includes religious, philosophical, secular, and scientific texts. The Vedas, Brahmanas, Aranyakas, Upanishads, Dharmasutras, Dharmashastras, epics, Puranas, Buddhist texts, Jain texts, Sangam literature, and secular works collectively provide information about ancient society. The Rigveda gives insights into early Vedic society, kinship, political institutions, occupations, religious practices, and