Whether or not the Aryas were racists, Hitler and the white supremacists had no business stealing their name. Nor did any of the more-or-less respectable European histories that discussed "Aryan" migration to the continent.
Modern research confirms William Jones' surmise that Sanskrit shares a common linguistic ancestor with Greek, Latin, German and many other European languages. But the research has gone further and reconstructed some of the stages that the ancestral languages passed through as they developed and divided.
Arya is one of many words that are found in both the Rigveda and in the Zorastrian religous text, the Avesta. So it looks as if the Rigvedic and Avestan languages developed from a common ancestor - a language that could be called "Proto-Indo-Iranian" or "Proto-Aryan". But this language was already distinct from the branches of the Indo-European family that became the languages of Europe. The mutual grandmother of all these languages might be called "Proto-Indo-European." Its partially reconstructed vocabulary is suggestive of life in steppe country, such as might be found in central Asia.
The speakers of "Proto-Indo-European" do not seem to have called themselves Aryas. So Persian and Sanskrit and and Urdu and Hindi and Bengali can be called "Aryan" languages but German and English and French and Latin and Greek cannot1. Which might have been guessed even without a century and a half of scholarship from the plain fact that the word "Aryan" didn't exist in any European language until Max Muller put it there.
The first Aryas were probably nomads. Their wealth was in cattle and their strength was in horse-drawn chariots. Fire linked them to the cosmos. Fire sacrifices were mediated on earth by the Brahmins, and in heaven by the fire god Agni. Sometimes the sacrificial object was an animal; sometimes it was a vegetarian dish, or flowers, or incense. Sometimes it was the mysterious substance called soma, which perhaps was a hallucinogenic drink brewed from Himalayan herbs.
The gods of classical and modern India were mostly unknown to the Aryas. The Rigvedic Creation Hymn bulges with philosophical speculation. But most Rigvedic prayers were for simple things - for wealth, and for victory in war. If the Vedas had a more profound message than this, it was mostly held in secret lore that only emerged when the Upanishads were composed, perhaps at the beginning of the first millennium BC.
The world of these texts is not the world of the first Vedas. They are filled with references to places on the Ganga and its tributaries. Afghanistan and the north-western Punjab – familiar country to the writers of the Rigveda – are now spoken of as alien territory. Perhaps a drying-up of the Indus basin had forced the Aryas south-eastwards. Or perhaps a new political grouping had stolen the show in the north-west.
In any event, the Aryas picked up the trick of rice cultivation from the Gangetic people, and the Ganga became their river of life, capable of washing away all sins. The forests became places of refuge, where Aryan sages went to meditate. It seems an odd habit for cowboys who followed the fire-god Agni, devourer of forests. Perhaps it was another thing that they learned from the Gangetic natives.
New names began to appear in the texts; the names of places in the mountains. Garhwal became Dev Bhoomi - the Land of the Gods. The old Aryan homelands of the northwest were forgotten.
There are other theories of course. That the Aryas entered India through Garhwal; that Aryas have lived in India for as long as humans have been human; that the standard history is a fairy tale told by Europeans to confuse the victims of colonialism; that scepticism about the standard theory is a fairy tale put about by Hindu nationalists to confound Muslims.
Facts are scarce. Anyone gazing on the undeciphered inscriptions from the first Indus cities would do well to suppose that they read:
Look on my works, ye scholars, and be humble.