Indo-Aryan migrations
The neutrality of this article is disputed.
The Aryan invasion theory was first put forward by German Indologist Friedrich Max Müller and others in the mid 19th century. This theory is contentious, for both political and historical reasons, but is currently generally accepted by most historians.
The theory holds that a Caucasian race of nomadic warriors known as the Aryans, originating in the Caucasus mountains in Central Asia, invaded Northern India and Iran, somewhere between 1800 and 1500 BC. The Invaders entered the Indian sub-continent from the mountain passes of the Hindu-Kush mountains possibly on horseback, bringing with them the domesticated horse into the sub-continent. The theory further proposes that this race displaced the indigenous Dravidian people and their Indus Valley Culture, and that the bulk of the indigenous people moved to the Southern reaches of the subcontinent. The Aryans brought with them their own Vedic religion, which was codified in the Vedas around the 1000 BC. Upon arrival in India, the Aryans abandoned their nomadic lifestyle and intermixed with the Dravidians remaining in the north of India. The victory of the Aryans over the Indus Valley Civilization was quick and complete, resulting in the complete domination of Aryan culture and language over the northern part of the subcontinent and considerable influence on parts of the south.
At this time most historians accept the theory, although the idea of a large-scale invasion that was prevalent around 1900 has given way to some extent to the idea of a much more modest invasion, in which the Aryans either merged in with the existing population or formed its upper layer.
This theory has recently been challenged by certain individuals who believe that no such migration or invasion occurred, and that the Indus Valley civilization was the civilization described in the Vedas.
Transformation to Aryan Migration Theory
For the invasion theory to be viable, the Aryans would have had to discover mountain passes among the treacherous Hindu-Kush mountains, most of which are snow free only three months a year. The Aryan invaders, being a nomadic people would be far smaller in number to the Indus valley civilization, which was spread over an area greater than 1.8 million square kilometers with an estimated population greater than the combined populations of all the other river civilizations at that time except ancient China. They would then have to quickly and completely rout an advanced civilization living in fortified cities over a large geographic area and impose thier culture on the local population without leaving any physical traces of themselves.
In addition, there are practically no archaeological signs of an invasion, nor oral or written legends of an invasion. This led to the modification of the Aryan invasion theory into the Aryan Migration Theory. It is much more likely that Aryan migrants found mountain passes and entered the sub-continent during the snow free months and settled within or close to the Indus valley civilization. Multiple waves of migration are possible, causing intermingling of the immigrant and local populations. There may have been significant exchange and assimilation of culture and language on both sides. The immigrants may have travelled back and forth to thier orignal lands taking language and culture to other Indo-European peoples, especially Ancient Persia. Human skeletal remains excavated from sites of the Indus Valley civilization shows a mixed ethnic composition similar to the present, showing support for migration rather than an invasion.
A Spectrum of Positions
Positions regarding The Aryan Invasion or Migration Theory vary widely on both sides from the reasonable to the fantastic. Also there is no clear cut division between Pro-Invasion and Anti-Invasion camps. Occasionally claims made by either camp may be accepted by the opposing camp. Over two thousand Indus Valley sites have been unearthed but only five percent of them have been excavated. Both camps adjust thier positions to accomodate new evidence that pours in from fresh excavations. A serious student interested in this aspect of ancient Indian history would read positions from both sides looking for internal consistency, verifying facts and ensuring that a stated position has not been invalidated by recent findings.
Evolution of the theory
The theory was first proposed in the nineteenth century only as a linguistic theory. Given that Europe had Indo-European speaking people, it was proposed that light skinned people invaded the subcontinent and subdued the aboriginal people and then mixed with them. The theory seemed resonable, given the contemporary history of European colonization. The aboriginal occupants of India were assumed to be primitive and the achievements of ancient India was credited to the invading Aryans. Later in the 1920's the Indus valley civilization was discovered, which was obviously extremely advanced for its time with planned cities, standardized system of weights and bricks, etc. The theory was modified to say that the nomadic Aryans had overthrown an advanced urban civilization. From this point on, the arguments center around differences or similarities between the Indus valley and Rig Vedic cultures.
Focus of Offered Evidence
The pro-invasion camp primarily focuses on showing that the Rig-Vedic culture is patoral, external to the Indian sub-continent and that a chronological gap exists between the Indus valley and the Rig Vedic cultures.
The anti-invasion camp focuses on stressing that the Rig-Vedic culture is native to the sub-continent, urban in nature and a chronological peer of the Harappan culture, perhaps they are the same culture.
The individual arguments may focus on linguistics, use of metals, domestication of horses or differences in described geography, but currently the basic focus is to identify with or against the Indus valley civilization.
Evidence for and against an invasion
Although there is very little archaeological evidence for an invasion (resulting in the transformation of the theory to a migration), there are a variety of arguments supporting either an Aryan migration or a continuous Indus Valley culture.
The linguistic divide is one of the strongest pieces of evidence supporting a migration. North Indian languages derived from Sanskrit are part of the Indo-European family of languages; the languages of south India belong to a different linguistic family, the Dravidian languages, with Tamil, a very distinct language in its own right (with literature and tradition nearly as ancient as Sanskrit, and disjoint from the Vedic), as the probable root of linguistic evolution.
While Dravidian languages are primarily confined to the south of India, there is a striking exception: the Brahui, which is spoken in the Indus Valley area, indicating that Dravidian languages were formerly much more widespread and were supplanted by the incoming Indo-European languages such as Sanskrit.
Another major argument offered against identifying the Indus Valley civilization with a continuous, indigenous Vedic civilization is that the society described in the Vedas is primarily a pastoral one, whereas the Indus Valley civilization was heavily urbanized. And that few of the elements of such an urban civilization (e.g., temple structures, sewage systems) are described in the Vedas.
However, the Rig Veda does contain the phrases: city's lord [Rig Veda 1:173], shrine [Rig Veda 9:113], ship with a hundred oars [Rig Veda 1:116] and iron forts [10:101]. So the Vedic soceity may not have been pastoral as was previously believed.
Recently, the excavation of Dholavira in the Gujarath province of India is claimed to shows a city that is consistent with vedic principles of city planning: arameshthina, madhyamesthina and avameshtina or upper, middle and lower cities [1].
Another piece of evidence mentioned in support of the invasion theory was the absence of horses in the Indus Valley civilization, while the Vedas make frequent mention of the horse. (The earliest domestication of the horse and the first use of horses in South Asia is a topic of great dispute.) However, the above arguments are weakened by the fact that the horse was not absent from the sites at Lothal, Surkotda and Kalibangan.
Similar weight has been placed on differences in the types of metals used in either civilization; the importance of the bull to the Indus Valley civilization as evidenced by imagery in seals and pottery in contrast to the Vedic cow-worship; the importance of the tiger in the Indus Valley civilization and its absence in the Vedic texts; and the heavy consumption of fish by the Indus Valley dwellers in contrast to the virtual absence of fish in the Vedas.
Opponents of the theory point out that the bull is mentioned numerous times in the vedas (next only to the horse), for example verses comparing Soma to the bull [Rig Veda 1:32, 9:92] and Exploits of Indra [Rig Veda 1:33, 7:24, 10:86]. Cow worship is not vedic, it originated in later Hinduism during the time of Krishna the cowherd. There are no verses in the vedas that speak about cow-worship. Verses mentioning fish do exist in the Rig Veda [7:18, 10:68] and the tiger is mentioned in the Yajur Veda [4:4, 5:3, 6:2, 7:7]. The Rig Veda mentions Iron [4:27], gold [4:37] and metal [10:53] numerous times indicating that the Vedic people were not as primitive as previously thought.
Opponents of the theory state that evidence in the Vedas points to a considerably earlier dating of the text. As an example, they argue that the positions of stars described in the Vedas occurred in 3500 to 4000 BC and point out that there is no account in the text of an invasion, of a great migration, or of an ancestral homeland in Central Asia.
There is, however, considerable description of a river Saraswati. Recent geological evidence (taken from satellite photographs) has uncovered the existence of a dry riverbed -- the Hakra River -- going through the Punjab area in the Indian subcontinent.
A few historians believe this river is the Saraswati described in the Vedas. Many of the archaeological Indus Valley sites lie along the remains of this riverbed, suggesting that the Indus Valley civilization may have flourished between these two rivers. Around 1900 BC, however, the Hakra river appears to have dried up (due to earthquakes and the shifting of the path of the tributary Yamuna river, which turned from feeding the Hakra to feeding the Ganges), causing the decline of the Indus Valley civilization.
Proponents of the theory of Aryan invasion argue that the identification of the Saraswati with the Hakra would lead to inconsistencies, and that the Saraswati is very probably a particular river in Afghanistan, that is known to have had a very similar name. They also point to the linguistic and religious similarities between the Vedas and early Iranian sacred literature such as the Avesta. The languages and the names of gods are very similar and both involve the ritual drinking of Soma.
The issue might be settled definitively by the deciphering of the many seals found at Indus Valley sites, which are written with an unknown script. If it were a Dravidian script this would confirm the theory that an indigenous culture was supplanted by an outside one. If it were Indo-Aryan it would support the alternative claims. However, the script remains undeciphered. Attempts to translate the script into some form of Sanskrit have been notable failures.
Politics
Like much of history, this question is immensely politically charged. Followers of the Hindu nationalist Hindutva movement very much wish to dispense with the Aryan invasion theory in favor of a continuous, ancient, and sophisticated Vedic civilization. In contrast there are many South Indians who have adopted the 'Dravidian' identity as a matter of ethnic pride.
Rejection of the theory by some proponents of Hindutva might also be motivated by the fact that the Aryan Invasion theory indicates that the Indian caste system was probably originally a means of social engineering by the Aryans to establish and maintain a superior position compared to the Dravidians in Indian society. This is a source of discomfort for some. The dominance in post-independence India of socialist accounts of history meant that this view prevailed for many years in Indian universities. The recent emergence of Hindutva as a significant force in Indian politics, and the consequent desire of some for a fantastically glorious historical past, is perhaps the more likely cause of changing attitudes rather than sound archaeology.