In the preceding section, we have come across the wide variation of the different groups and sub-groups of Indian tribes based on permanent traits like geographical, linguistic, racial, size, and acquired traits like the economy or subsistence pattern and degree of incorporation into the Hindu society. There are many factors which lead to this great degree of variations which are enumerated below:
Migration
India had experienced different waves of movement of populations dating back to thousands of years. The earliest known population movement is that of the Aryans who were a group of pastoralists who are said to have migrated from Iran through Afghanistan in around 1500 B.C. from the north-western side of the Indian subcontinent. They eventually displaced the Indus Valley culture and made this region their home.
In much later periods of history the invasion of Greeks under Alexander the Great was followed by other invasions from the West and Central Asia like those of the Scythians known as the Sakas in India; the Yue-Chi from Central Asia, the Arabs from Baghdad in the eighth century; the Turks of Afghanistan in the thirteenth century and finally the Central Asian invaders under Babur in the sixteenth century which laid the foundations of the Mughal rule in India.
Apart from these invasions, migrant communities had come to India as merchants, traders religious practitioners and even as slaves.
This is the main cause behind the wide variety of racial and linguistic strains evident in the racial and cultural mosaic of India.
Acculturation and assimilation
The migrants and the original inhabitants have been living in close contact with each other for centuries. The interaction between the two led to much acculturation as well as assimilation over the years. As a result, many new traits find their way into the cultural mosaic of the immigrant communities and many traits also die out leading to the variations in the culture of the two sides.
Geography or the physical environment
The geographical or the physical environment of an area plays an important role in shaping the socio-economic conditions and cultural elements in the life of the people. For instance, the Bhotia of the eastern Himalayas follow Buddhism while those of the central Himalayas are Hindus due to the influence of the neighbouring communities. There is an obvious difference in the dress between the Gujjars settled in the cold region in the Jammu and Kashmir and those inhabiting the arid region of Rajasthan. The people living in the hilly region practice the shifting and terrace method of cultivation whereas those of the plains practice agriculture.