The Indus Valley Civilization (Mature period 2600–1900 BCE), was an ancient civilization that flourished in the Indus River basin. Primarily centred in India (Gujarat, Haryana and Rajasthan) and today's Pakistan (Sindh and Punjab provinces), it extended westward into the Balochistan province of Pakistan. Remains have been excavated from Afghanistan, Turkmenistan and Iran, as well.
Historically part of Ancient India, it is one of the world's three earliest urban civilizations along with Mesopotamia and Ancient Egypt. The mature phase of this civilization is technically known as the Harappan Civilization.

There are several theories as to the origin of the Indus Valley civilization. The earliest hypothesis was that it was an early form of a Vedic and early Sanskrit civilization which would come to dominate most of South Asia, which was presumed to have been characterized by influence from Indo-European migrations. However, this theory began to be rejected when no signs of the traditional culture associated with the Vedas was uncovered in that of the Indus Valley. The absence of horses amongst the many realistic representations of animals was also considered significant, considering the importance of horses and chariots to the culture described in the Vedas. Detailed bone analysis has revealed that the horse itself was introduced to the subcontinent only at the beginning of the second millennium B.C., which contributes to the chronological problem with this theory.Finally, the concept of urban life which dominates the Indus Valley civilization is foreign to the more rural lifestyle which is described in the Vedas.

The next theory put forward was that the civilization was of proto-Dravidian origin.This theory was first proposed by researchers from Russia and Finland who attempted to show that Indus valley symbols could be derived from the Dravidian language group. Today, the Dravidian language family is concentrated mostly in southern India and northern Sri Lanka, but pockets of it still remain throughout the rest of India and Pakistan (the Brahui language), which lends credence to the theory. Finnish Indologist Asko Parpola concludes that the uniformity of the Indus inscriptions precludes any possibility of widely different languages being used, and that an early form of Dravidian language must have been the language of the Indus people. However, the proto-Dravidian origin theory is far from being confirmed due to an emphasis on linguistic connection while evidence of a broader cultural connection remains to be found.
The three main phases of the Indus Valley Civilization are:
Early Harappan (Integration Era)
Mature Harappan (Localization Era)
Late Harappan (Regionalization Era)

Early Harappan

The Early Harappan Phase lasted from 3300 BC to 2800 BC. It is related to the Hakra Phase, identified in the Ghaggar-Hakra River Valley. The earliest examples of the Indus script date back to 3000 BC. This phase stands characterized by centralized authority and an increasingly urban quality of life. Trade networks had been established and there was also domestication of crops. Peas, sesame seeds, dates, cotton, etc, were grown during that time. Kot Diji represents the phase leading up to Mature Harappan Phase

Mature Harappan

By 2600 BCE, the Early Harappan communities had been turned into large urban centers.Such urban centers include Harappa, Ganeriwala, Mohenjo-daro in modern day Pakistan and Dholavira, Kalibangan, Rakhigarhi, Lothal in modern day India. In total, over 1,052 cities and settlements have been found, mainly in the general region of the Indus Rivers and their tributaries.
The following features of the Mature Phase were more prominent:

Cities





A sophisticated and technologically advanced urban culture is evident in the Indus Valley Civilization making them the first urban centers in the region. The quality of municipal town planning suggests the knowledge of urban planning and efficient municipal governments which placed a high priority on hygiene, or, alternately, accessibility to the means of religious ritual.
As seen in Harappa, Mohenjo-daro and the recently partially excavated Rakhigarhi, this urban plan included the world's first urban sanitation systems. Within the city, individual homes or groups of homes obtained water from wells. From a room that appears to have been set aside for bathing, waste water was directed to covered drains, which lined the major streets. Houses opened only to inner courtyards and smaller lanes. The house-building in some villages in the region still resembles in some respects the house-building of the Harappans
The ancient Indus systems of sewerage and drainage that were developed and used in cities throughout the Indus region were far more advanced than any found in contemporary urban sites in the Middle East and even more efficient than those in many areas of Pakistan and India today. The advanced architecture of the Harappans is shown by their impressive dockyards, granaries, warehouses, brick platforms and protective walls. The massive walls of Indus cities most likely protected the Harappans from floods and may have dissuaded military conflicts
Most city dwellers appear to have been traders or artisans, who lived with others pursuing the same occupation in well-defined neighborhoods. Materials from distant regions were used in the cities for constructing seals, beads and other objects.

Science



The people of the Indus Civilization achieved great accuracy in measuring length, mass, and time. They were among the first to develop a system of uniform weights and measures. Their measurements are said to be extremely precise; however, a comparison of available objects indicates large scale variation across the Indus territories. Their smallest division, which is marked on an ivory scale found in Lothal, was approximately 1.704 mm, the smallest division ever recorded on a scale of the Bronze Age. Harappan engineers followed the decimal division of measurement for all practical purposes, including the measurement of mass as revealed by their hexahedron weights. The brick weights were in a perfect ratio of 4:2:1.
Unique Harappan inventions include an instrument which was used to measure whole sections of the horizon and the tidal lock. In addition, Harappans evolved some new techniques in metallurgy and produced copper, bronze, lead and tin. The engineering skill of the Harappans was remarkable, especially in building docks after a careful study of tides, waves and currentsThe early Harappan periods, had knowledge of proto-dentistry.

Arts and culture





Many crafts "such as shell working, ceramics, and agate and glazed steatite bead making" were used in the making of necklaces, bangles, and other ornaments from all phases of Harappan sites and some of these crafts are still practiced in the subcontinent today.Some make-up and toiletry items (a special kind of combs (kakai), the use of collyrium and a special three-in-one toiletry gadget) that were found in Harappan contexts still have similar counterparts in modern India.Terracotta female figurines were found (ca. 2800-2600 BCE) which had red color applied to the "manga" (line of partition of the hair).
Seals have been found at Mohenjo-daro depicting a figure standing on its head, and another sitting cross-legged in what some call a yoga-like pose.
A harp-like instrument depicted on an Indus seal and two shell objects found at Lothal indicate the use of stringed musical instruments. The Harappans also made various toys and games, among them cubical dice (with one to six holes on the faces), which were found in sites like Mohenjo-Daro.There is also evidence of seals, toys, games and stringed musical instruments in the Indus Valley.

Trade and transportation

The Indus civilization's economy appears to have depended significantly on trade, which was facilitated by major advances in transport technology. These advances included bullock carts that are identical to those seen throughout South Asia today, as well as boats. Most of these boats were probably small, flat-bottomed craft, perhaps driven by sail, similar to those one can see on the Indus River today; however, there is secondary evidence of sea-going craft.

Agriculture

The major cultivated cereal crop was naked six-row barley, a crop derived from two-row barley. However, not much information is available on the farmers and their agricultural methods.

Writing or symbol system





over 400 distinct Indus symbols (some say 600) have been found on seals, small tablets, or ceramic pots and over a dozen other materials, including a "signboard" that apparently once hung over the gate of the inner citadel of the Indus city of Dholavira.
The Indus Valley Civilization is often characterized as a literate society on the evidence of these inscriptions, this description has been challenged on linguistic and archaeological grounds

Religion







In view of the large number of figurines found in the Indus valley, it has been widely suggested that the Harappan people worshipped a Mother goddess symbolizing fertility.Some Indus valley seals show swastikas which are found in later religions and mythologies, especially in Indian religions such as Hinduism and Jainism. The earliest evidence for elements of Hinduism are present before and during the early Harappan period. Phallic symbols resembling the Hindu Siva lingam have been found in the Harappan remains.
Many Indus valley seals show animals. One famous seal shows a figure seated in a posture reminiscent of the Lotus position and surrounded by animals was named after Pashupati (lord of cattle), an epithet of Shiva and Rudra.In the earlier phases of their culture, the Harappans buried their dead.later, especially in the Cemetery H culture of the late Harrapan period, they also cremated their dead and buried the ashes in burial urns, a transition notably also alluded to in the Rigveda, where the forefathers "both cremated (agnidagdhá-) and uncremated (ánagnidagdha-)" are invoked


Late Harappan Phase

The signs of a gradual decline of the Indus River Valley Civilization are believed to have started around 1800 BC. By 1700 BC, most of the cities were abandoned. However, one can see the various element of the Ancient Indus Valley Civilization in later cultures. Archaeological data indicates the persistence of the Late Harappan culture till 1000-900 BC. The major reasons of the decline of the civilization are believed to be connected with climate change. Not only did the climate become much cooler and drier than before, but substantial portions of the Ghaggar Hakra river system also disappeared.