As a child we would ask our grandfather why we are called Saraswat Brahmin and why do we eat fish. He would tell us what his father told him that our ancestors came from Saraswati river which dried up forcing our migration. Some of the Saraswats went to Kashmir like Nehru, others went to Bengal. Some left Bengal and came to Goa and then moved to Karnataka and Maharashtra especially after advent of Portuguese.
My father was was scientist so would say there is no scientific evidence for existence of Saraswati River which is mentioned in Rigveda 70 times. But he did not even subscribe to Aryan Invasion theory saying no evidence for the same except Maxmuller hypothesis which he questioned saying Aryans who had no linguistic background can develop Rigveda in 300 years (Other civilizations have shown that it takes at least 700-750 years and that too not with that level of grammar and meter would take far more) and they would have referred to Sindhu River (its appears only 14 times) or Ganga (only once).
And then our teachers would talk about mythical Saraswati river which met Ganges but vanished now. So I would try to find out whatever I could about that mighty river in Vedas. Of course we knew simply because there Pusphak airplane in Ramayana does not mean people had planes exactly like H.G. Wells 1895 novel about Time Machine- can exist, as Einstein later proved in 1905 speed of light is ultimate so time machine can not exist at least in the universe we know
And then ISRO–NASA used remote sensing satellites to study buried river channels in the Thar Desert. Paleochannels found in this study are available on ISRO’s Bhuvan portal.
The image at the top is AI-generated to represent what the Saraswati — a mighty river from the Vedic period — may have looked like based on scientific estimates of its scale and environment.
A detailed scientific timeline of this research is available here: Scientific Timeline – Rediscovery of the Saraswati River.
That proved beyond doubt existence of mighty Saraswati river flowing from Himalayas and meeting Arabian Sea in Rann of Kutch, with Satlej and Yamnua as its subsidiaries. Technonic shift made Sajtlej move west meeting Sindhu and Yamuna moving east meeting Ganges. These dried Saraswati river leading to migration of all, not only Saraswat Brahmins. And as Vedas were passed from generation to generation with oral recitation this fact was tranmitted through literally hundred generation through world of mouth. So my grandfather was right and evidence available would have met the strictest scientific standards of my father.