The emerging alternative to the Aryan Invasion Theory may be summarized as follows.  In the 6th millennium BC, the Proto-Indo-Europeans were living in what is now Panjab, Haryana and western Uttar Pradesh, speaking a variety of mutually comprehensible dialects, and tending cattle as well as practising agriculture.  Due to demographic growth, internal conflicts and the occasional economic crisis, some of them moved out through the Khyber pass to Margiana and Bactria, which was to remain a frontier zone of Indian culture for millennia.  From there, some of them moved on to the Caspian coast, while others moved east to become the Tokharians.  During this stay in Central Asia, they adapted to the local way of life, growing millet and domesticating the horse, a skill which was soon communicated back to the motherland.  The group which separated earliest from the rest was the one which took the oldest form of the IE language along: we encounter them by 2,000 BC in Anatolia.

The next move of the IE settlers in Central Asia, by 4,500 BC, brought them across the Urals and the Volga into Europe.  By internal development and because of interaction with ever new native populations, their dialects changed and differentiated.  Expanding ever more westward and southward, they broke into the Old European civilization of the Balkans and overran Anatolia.  Another group developed its own distinctive culture in northern Central Europe, and was poised to overrun Western Europe and the British Isles.

Meanwhile in India, civilization made great strides, writing was invented ca. 3,500 BC (unfortunately too late for the emigrants to take along), astronomy perfected, cities built of ever greater urbanistic quality.  The language, still spoken only in a limited area, had developed the characteristic traits of Indo-Iranian, except in some outlying regions where older forms of IE were preserved, among them Proto-Bangani.  Priests composed hymns to the gods and learned the hymns composed by their teachers and colleagues by heart, accumulating a tradition known as Veda.

In the northern Indus basin, the Indo-Iranians started fighting amongst each other, and one result was that several factions followed the beaten track to Afghanistan and beyond. We meet them in history as the Iranians, who had built strongholds in Bactria whence their adventurers trekked north and then east as well as west, turning the whole of Central Asia into an Iranian Lebensraum; much later, they also conquered the countries to the west and southwest as far as Mesopotamia.  They often clashed with the Indians, who had just reached the apogee of civilization with their large and numerous well-planned cities, and who tried to gain control over the Afghan mining centres.  Later, perhaps already as a result of the crisis which sounded the death-knell of the magnificiant Harappan cities, more people migrated from India to become the West-Asian Indo-Aryans.  Having moved through Margiana to the south side of the Caspian Sea, they mixed with Hurrites, Kassites and others, and pushed as far west as Palestine, making their mark for a few centuries (18th-12th century BC) in different parts of West Asia before disappearing through assimilation,

In the southern Indus-Saraswati basin, the Indo-Aryans met the Dravidians whom they assimilated.  However, Dravidian language and culture were preserved thanks to Dravidian colonists who had started settling in the south, in their turn assimilating the Veddoid and other native tribals. In a parallel movement, Indo-Aryans were colonizing India’s interior, assimilating the tribals they encountered, except in the less accessible corners where they left them to their traditional way of life.  This movement from the northwest to the rest of India accelerated with the decline of the Harappan cities, yielding essentially the very distribution of languages over the Indian territory which exists till today.

This model will certainly need amendments and corrections, but it is better able to explain the data than the dominant Kurgan-to-India invasionist model.