I heard that Hindus believe that all Vedic-era people originated in Bhārat. Is this a cultural belief or is it from scripture?
The below non-Answers are "arguments against the mainstream theory" rather than Answers to the above question. Upvoting them is dishonest propagandizing.
No not only to the Hindus but it is well known in rest of the world that Aryan Invasion Theory is wrong.
It looks like you are more impressed with the 120 year myth created by F. Max Muller in 1848. And is biased towards western Indologist ,ignoring new research conducted by Hindu scholars and their opinions despite the solid evidence provided by them and not mentioning thousands of articles present over the Internet showing that Aryan Migration Theory is Debunked.
Aryan Invasion Theory was reinforced by western scholars on Hindu people (Hinduism) and on the rest of the world and became the accepted history of Hinduism until some time back.
It is accused that the theory is put forward for racist ideas: These are some of the points I have compiled.
The Indus valley culture was pronounced pre-Aryans for several reasons that were largely part of the cultural milieu of nineteenth century European thinking. As scholars following Max Muller had decided that the Aryans came into India around 1500 BC, since the Indus valley culture was earlier than this, they concluded that it had to be pre-Aryan. Yet the rationale behind the late date for the Vedic culture given by Muller was totally speculative. Max Muller, like many of the Christian scholars of his era, believed in Biblical chronology. This placed the beginning of the world at 400 BC and the flood around 2500 BC. Assuming to those two dates, it became difficult to get the Aryans in India before 1500 BC.
The Vedic culture was thus said to be that of primitive nomads who came out of Central Asia with their horse-drawn chariots and iron weapons and overthrew the cities of the more advanced Indus valley culture, with their superior battle tactics. It was pointed out that no horses, chariots or iron was discovered in Indus valley sites.
These are the points mentioned By David Frawley in his book.
1) This was how the Aryan invasion theory formed and has remained since then. Though little has been discovered that confirms this theory, there has been much hesitancy to question it, much less to give it up.
2 ) Further excavations discovered horses not only in Indus Valley sites but also in pre-Indus sites. The use of the horse has thus been proven for the whole range of ancient Indian history. Evidence of the wheel, and an Indus seal showing a spoked wheel as used in chariots, has also been found, suggesting the usage of chariots.
3) Moreover, the whole idea of nomads with chariots has been challenged. Chariots are not the vehicles of nomads. Their usage occured only in ancient urban cultures with much flat land, of which the river plain of north India was the most suitable. Chariots are totally unsuitable for crossing mountains and deserts, as the so-called Aryan invasion required.
Further excavation revealed that the Indus Valley culture was not destroyed by outside invasion, but according to internal causes and, most likely, floods. Most recently a new set of cities has been found in India (like the Dwaraka and Bet Dwaraka sites by S.R. Rao and the National Institute of Oceanography in India) which are intermediate between those of the Indus culture and later ancient India as visited by the Greeks. This may eliminate the so-called dark age following the presumed Aryan invasion and shows a continuous urban occupation in India back to the beginning of the Indus culture.
In other words there is no racial evidence of any such Indo-Aryan invasion of India but only of a continuity of the same group of people who traditionally considered themselves to be Aryans.
According to this theory, the Vedic people were nomads in the Punjab, coming down from Central Asia. However, the 'Rig Veda' itself has nearly 100 references to ocean (samudra), as well as dozens of references to ships, and to rivers flowing in to the sea. Vedic ancestors like Manu, Turvasha, Yadu and Bhujyu are flood figures, saved from across the sea. The Vedic God of the sea, Varuna, is the father of many Vedic seers and seer families like Vasishta, Agastya and the Bhrigu seers. To preserve the Aryan invasion idea it was assumed that the Vedic (and later Sanskrit) term for ocean, samudra, originally did not mean the ocean but any large body of water, especially the Indus river in Punjab. Here the clear meaning of a term in 'Rig Veda' and later times - verified by rivers like Saraswati mentioned by name as flowing into the sea - was altered to make the Aryan invasion theory fit. Yet if we look at the index to translation of the 'Rig Veda' by Griffith for example, who held to this idea that samudra didn't really mean the ocean, we find over 70 references to ocean or sea. If samudra does not mean ocean, why was it translated as such? It is therefore without basis to locate Vedic kings in Central Asia far from any ocean or from the massive Saraswati river, which form the background of their land and the symbolism of their hymns.
In a article Frawley also talks about Aryan-Dravidian divide ,this is what he says.
Dravidian history does not contradict Vedic history either. It credits the invention of the Tamil language, the oldest Dravidian tongue, to the rishi Agastya, one of the most prominent sages in the Rig Veda. Dravidian kings historically have called themselves Aryans and trace their descent through Manu (who in the Matsya Purana is regarded as originally a south Indian king). Apart from language, moreover, both north and south India share a common religion and culture. Prior to Vedic Sanskrit there may have been a language that was the basis of both the Dravidian and Sanskritic languages in India.
Above all read this article - Harvard University’s international scandal unravels a global Hindu conspiracy.
North & South Bharatiyas Share Tissue Antigens, Distinct From Those of Europeans.
North & South Bharatiyas Share mtDNA, Which Is Distinct From That of Europeans.
Conclusion: The stark lack of similarities in the gene pools of the Indian subcontinent and Europe, vividly evident in the mtDNA and the MHC complex, destroys any ' Aryan invasion' notions, and confirms the genetic uniformity of peoples of the Indian subcontinent. Chandrakant Pansé, Professor of Biotechnology
In addition to @SwiftPushkar's excellent answer:
Argument A1)
http://nature.com/articles/srep26555 from "nature" journal established that Harappan civilization is 8000 years old and collapsed due to weaker monsoon and climate change, not due to any invasion
Argument A2)
B. B. Lal is a renowned archeologist and former Director General of the Archaeological Survey of India (ASI) who has written many books and papers on the Aryan issue.
(1) Please read his reference book published in 2015 "The Rigvedic People: Invaders?/ Immigrants? Or Indigenous?" by B B lal https://www.amazon.in/Rigvedic-People-Invaders-Immigrants-Indigenous/dp/8173055351
(2) The summary of his book can be read in his interview here, where he debunks all the flaws in how marxists and western historians reached to their flawed conclusions http://web.archive.org/web/20171124044705/https://www.newsgram.com/no-evidence-for-warfare-or-invasion-aryan-migration-too-is-a-myth-b-b-lal
This book debunks aryan migration theory(AMT)
Argument A3)
See this genetic study by a CCMB instiute which debunks AMT/AIT theory https://timesofindia.indiatimes.com/india/Aryan-Dravidian-divide-a-myth-Study/articleshow/5053274.cms
Argument A4)
pro-AMT
(disclaimer:Now, my next discussions are not links from journals and peer reviewed books, but from newspaper and sites, but this is for addon discussion.) the article by Tony joseph on "How genetics is settling the Aryan migration debate" in year 2017 supports aryan migration theory http://www.thehindu.com/sci-tech/science/how-genetics-is-settling-the-aryan-migration-debate/article19090301.ece
anti-AMT
(disclaimer:Now, my next discussions are not links from journals and peer reviewed books, but from newspaper and sites, but this is for addon discussion.) But that Hindu article by Tony joseph and similar articles have been comprehensively critiqued by researchers in 2018 study
http://indiafacts.org/propagandizing-aryan-invasion-debate-rebuttal-tony-joseph/
argument A5)
also see Aryan Migration theory—evidence for and against it in the Vedas
argument A6)
Racial intepretation of "Dravida" term as "non-aryan" by western historians, is debunked in this paper https://www.academia.edu/1573411/Vedic_Roots_of_Early_Tamil_Culture and summarised in this answer https://hinduism.stackexchange.com/a/2321/13287
argument A7)
Dr. B R Ambedkar also debunked Arya Invasion/Migration Theory https://archive.org/details/in.ernet.dli.2015.282497 see chapter 4 (additional urls http://www.opindia.com/2018/04/dr-ambedkar-rejected-aryan-invasion-theory-with-facts-and-logic and https://en.wikipedia.org/wiki/Who_Were_the_Shudras%3F ) . Dr. Ambedkar provides an alternative explanation of "shudras origination" , instead of racial (non-aryan) interpretation by western historians about shudras origination
Argument A8)
In the book "Indo-Aryan Controversy Evidence And Inference In Indian History Routledge ( 2005)" authored by "Edwin Bryant, Laurie Patton (Eds.)", published in 2005 ; the authors have in detail re-evaluated all the arguments pro and against the AMT till date in modern times, and then arrived the conclusion that AMT is false
Argument A9)
for detailed arguments by Stephen knapp, read here
https://www.stephen-knapp.com/death_of_the_aryan_invasion_theory.htm
book: "The Aryan Invasion Theory: The Final Nail in its Coffin"
https://www.amazon.in/Aryan-Invasion-Theory-Final-Coffin-ebook/dp/B00AEIHF2Y/ref=pd_typ_k_sp_1_2/259-1374969-7588913?_encoding=UTF8&psc=1&refRID=06Z8C3G0W65JZHPFN560
Argument 11) also related- see answers given in:
Aryan Invasion is a straw man. Westerners and mainstream Indian researchers and academics have moved on Aryan Migration. The "God of the sea" - Narayana occurs only in later scriptures - hard to explain if Rig Veda was produced by people to to whom the sea was important. Himalaya hardly finds mention in Rig Veda - once again showing the Western origin of the Aryas.
What the Puranas did to Magnificent gods like Mitra and Varuna (something absent from other Indo-European mythologies) shows that there was a cultural shift of Rig Vedic people after contact with Indians. Without any recourse to DNA - it is beyond a shadow of a doubt that there was a cultural migration from the Northwest to Afghanistan/Pakistan/NorthWest India to produce the foundational scripture - Rig Veda.
