Further Spread of Vedic Religion?

[tex mex]

Due to expansion and diffusion, the Vedic Religion spread from Northwest india to most of the Indian Subcontinent by 300 BC. You had the Sinhalese in Ceylon to the Kamboja in Kabul Valley adhering to this religion. From some sources, even some Dhivehis in Maldives practiced it. With diffusion of Buddhism and Jainism, the Vedic religion declined and evolved into Hinduism.
Today some aspects of Vedic Religion still survive, and is called Srauta. Its practitioners, are called Srautins, meaning they adhere to Sruti texts(sole focus on Vedas) instead of Smriti as Hinduism does. Some people in Kerala and Coastal Andhra still practice this culture but only very few. Hinduism is generally Smriti focused, while Vedic religion is Sruti focused.

How can we have a further spread of Vedic culture? Indian culture spread to Southeast Asia and Tarim Basin at a much later date as a joint package, it was more Buddhist and Smriti-oriented Hinduism. I don't think Srauta customs spread there OTL.
Some possible candidates include:
1. Burma. The Pyu tribes develop ties to Nanda Dynasty, and adopt Vedic rituals from them.
2. Bactria. The Bactria becomes a Mauryan Vassal, and the royal family there adopts Vedic rituals from Kamboja and Gandhara peoples.
3. Tibet. The Zhangzhung Kingdom in Western Tibet adopts Vedic rituals from Kashmir. They then spread it to Tibet Eastward
4. Tarim Basin. The Saka and Tocharian rulers adopt Vedic rites from Kashmir or from Bactria(assuming scenario 2 works) around AD 1.

Read more: https://en.wikipedia.org/wiki/Historical_Vedic_religion

Vedic Ritual: Agnicayana

 

[tex mex]

@herkles @Emperor-of-New-Zealand @Brahman @Emperor of Greater India

 

[Madhukar_Shah]

I mean it is essentially the perfect steppe religion- completely portable, no need for literacy, maintains uniformity over impossible distances.

The only problem is that the actual Vedas themselves were solidified after the consolidation of the tribes in India, and the system of rote memorization gave the system much of its stability. Perhaps anytime between 800 and 400 BC you have a Romani like exodus of vedic people's out of india- with that, I don't think it's impossible to have vedic religion spread quickly along the entirety of the Eurasian steppe.

I don't think after about 400 BC it could happen because by this point vedic rituals would be impossible to isolate from the whole cultural package, which is a lot less nomad friendly. But hey have it late enough, and you could have Huns bringing it deep into Europe. Of course just like in India, there's probably little chance of it remaining "purely" vedic, and the mythologies and cosmologies surrounding the rituals would continue to evolve and diversify.

 

[Metempsychosis]

I mean it is essentially the perfect steppe religion- completely portable, no need for literacy, maintains uniformity over impossible distances.

The only problem is that the actual Vedas themselves were solidified after the consolidation of the tribes in India, and the system of rote memorization gave the system much of its stability. Perhaps anytime between 800 and 400 BC you have a Romani like exodus of vedic people's out of india- with that, I don't think it's impossible to have vedic religion spread quickly along the entirety of the Eurasian steppe.

I don't think after about 400 BC it could happen because by this point vedic rituals would be impossible to isolate from the whole cultural package, which is a lot less nomad friendly. But hey have it late enough, and you could have Huns bringing it deep into Europe. Of course just like in India, there's probably little chance of it remaining "purely" vedic, and the mythologies and cosmologies surrounding the rituals would continue to evolve and diversify.

Hmm.

Maybe an Indian philosopher-prince goes full-tilt Akhenaten for Shiva/Vishnu or something and drives out a large group of Brahmins and Kshatriyas who end up going back into the steppe? IDK how India would develop an intolerance that would bring a bunch of Vedic traditionalists out.

Or maybe a Vedic traditionalist school of thought brings a bunch of clans who want to keep their rituals pure back onto the steppe?

 

[LostInNewDelhi]

don't think after about 400 BC it could happen because by this point vedic rituals would be impossible to isolate from the whole cultural package, which is a lot less nomad friendly.

The challenge of pre-literarcy is that you wouldn't have much evidence of this sort of thing even if it did happen but-- maybe the druids of Ireland and possibly Gaul and Britain, or various lore-memorizers and magicians among the Norse, indicate it's possible for some diffusion of pre-literate religious practices between mostly settled populations?

The populations would probably have to be close together though, so you'd probably still need an outpost of this culture somewhere off the Indian subcontinent (that seems to be OP's criterion). The Indus and Ganges both lead right back into the Himalayas and Hindu Kush; as an alternative to mountain travel, the Brahmaputra at least deposits you out into the ocean-- so maybe there needs to be some precocious development out in the Bengal area, and then further developments in Arakan. Maybe the timetable for adoption of rice plays into all this somehow

But hey have it late enough, and you could have Huns bringing it deep into Europe. Of course just like in India, there's probably little chance of it remaining "purely" vedic, and the mythologies and cosmologies surrounding the rituals would continue to evolve and diversify.

Wait a minute-- isn't this nearly what the Mitanni did out in the Near East, depositing an equestrian elite that expressed its prayers to "Indar"? I suppose it's not Vedic in the sense of operating on the scriptures as we know them, but something of its like has happened before.

Maybe an Indian philosopher-prince goes full-tilt Akhenaten for Shiva/Vishnu or something and drives out a large group of Brahmins and Kshatriyas who end up going back into the steppe? IDK how India would develop an intolerance that would bring a bunch of Vedic traditionalists out.

Well. Strictly speaking what separates the "Vedic" custom discussed here from what came later? A lot of things that were to be taken literally before are now primarily valued for their value in expressing some kind of abstraction. We went from ritual sacrifices for Agni to "agni" as a kind of abstraction for fire in all its uses-- uses for other things, no longer an end in itself.

So in that sense the "Atenist" thing would be to defy this abstraction and whatever philosophical edifices may be built on it. In other words, take away the Upanishads' interpretations, from which we derive the whole metaphysical vocabulary that later Hinduism uses, and what you're left with is... meat for the Fire God.

The uncertain authorship and practice of treating the clearly late coming Upanishads as "embedded" texts in the Vedas (or maybe that is how it went, when you're passing along the text down the oral-recitation chain, you add a little space for your footnotes?) means I have no list of people to kill in other to avoid this direction-- to be honest it may be inseparable from the process of oral transmission. You can turn your brain off and copy a written book letter by letter-- boom, inviolable text. But memorizing a massive scripture is a very involved process, how are people not supposed to think about the content and pass those on for the benefit of posterity? So maybe some *event*, like a freak astronomical or climactic occurrence, sets some kind of red line which declares certain lines of thought off limits.

 

[Madhukar_Shah]

Or maybe a Vedic traditionalist school of thought brings a bunch of clans who want to keep their rituals pure back onto the steppe?

Even the rigveda itself has no memory of any place west of Afghanistan, as far as they're concerned it's a whole new area.

I suppose it's not Vedic in the sense of operating on the scriptures as we know them, but something of its like has happened before.

The mitanni though came directly from BMAC, not from India first, so it's not an exact parallel iirc. And you're right, back then the religion was more like poet's consuming soma and improvising on ritual occasions than the rote memorization that characterises mature vedic practice.

 

[Brahman]

Vedic religion are a whole based heavily in India and Indian subcontinent. It is very difficult to have it be expanded out of there.

However, one possible way is that Indo Iranian religous split does not happen as such both Vedic and Avesta are considered the same and are thus much more prominent across the world

 

[prani]

Due to expansion and diffusion, the Vedic Religion spread from Northwest india to most of the Indian Subcontinent by 300 BC. You had the Sinhalese in Ceylon to the Kamboja in Kabul Valley adhering to this religion. From some sources, even some Dhivehis in Maldives practiced it. With diffusion of Buddhism and Jainism, the Vedic religion declined and evolved into Hinduism.
Today some aspects of Vedic Religion still survive, and is called Srauta. Its practitioners, are called Srautins, meaning they adhere to Sruti texts(sole focus on Vedas) instead of Smriti as Hinduism does. Some people in Kerala and Coastal Andhra still practice this culture but only very few. Hinduism is generally Smriti focused, while Vedic religion is Sruti focused.

How can we have a further spread of Vedic culture? Indian culture spread to Southeast Asia and Tarim Basin at a much later date as a joint package, it was more Buddhist and Smriti-oriented Hinduism. I don't think Srauta customs spread there OTL.
Some possible candidates include:
1. Burma. The Pyu tribes develop ties to Nanda Dynasty, and adopt Vedic rituals from them.
2. Bactria. The Bactria becomes a Mauryan Vassal, and the royal family there adopts Vedic rituals from Kamboja and Gandhara peoples.
3. Tibet. The Zhangzhung Kingdom in Western Tibet adopts Vedic rituals from Kashmir. They then spread it to Tibet Eastward
4. Tarim Basin. The Saka and Tocharian rulers adopt Vedic rites from Kashmir or from Bactria(assuming scenario 2 works) around AD 1.

I mean it is essentially the perfect steppe religion- completely portable, no need for literacy, maintains uniformity over impossible distances.

One way by which you can achieve this is by Making a significant number of Vedic Tribes turning to horse breeding instead of raising Cattle as the basis of their living, say they take this decision in the light of incessant warfare in Vedic India, The tribes in search of Pastureland go North wards and back into the steppe, because South Asia isn't so well suited for raising horses and eventually spread their faith amongst the other Iranic Tribes up north. I mean the Vedic Tribes would have the advantage of having larger horse herds than their Iranic cousins up north who are just making the transition from cattle to horse as the climate of the steppe went from being warm and wet to dry and cold making the task of raising cattle harder. It wasn't until the 800 BC did we see the modern day horse mounted nomads with their massive horse herds barreling down on cities in the middle east. So the Vedic tribes have a good 700 year advantage. They can conquer and subjugate not only the Iranic Tribes but also people beyond the Altai. Thereby turning the lands from Ukraine to Manchuria, Vedic in faith all you need is for the Vedic Aryan Tribes to switch from Cattle to horse and let mother nature take care of the rest. So instead of the Saka or the Sarmatians tribes you'll have Indic sounding tribes on the Pontic steppe, the butterflies of this are huge since the Eastern Slavs did absorb a large number of Iranic Tribes, The Mongols and the Turkic people would being their existence as a vassal of these Vedic Aryans or given their level of success these ethnic groups might not even exist.

 

[Jan Olbracht]

Iranic religion affected Slavic religion (Slavs adopted Iranic dualism, even Slavic word for god (bog) is of Iranic origin. So if steppe nomads are vedic instead then vedic influence indeed can reach as far as Central Europe.

 

[prani]

Vedic and Avesta are considered the same

You're not serious with this statement, the gathas are basically diss track on the Devas and vendidad basically contains yo Mama jokes on the Devas. Vendiad literally translates to "given against the Devas" meaning knowledge of the remedies against the Devas.
Yeah the Vedas make no mention of the ahuras or Asuras as being evil things that role is taken by Danava who are a category of Asura, it's only post Vedic that rakshasa and Asura becomes synonyms of although a scholar would know the difference. In rig Veda, indra Agni etc are all called as Ahuras or Asuras.

Besides Vedas and avesta represent Iranian/Aryans at two very different points in time, in their evolution, Vedas were written or rather composed by semi nomadic cattle breeders who came to India while avesta was written again rather composed by settled iranic people or atleast in the process of transitioning from a nomadic life to a settled one and a transition from a tribal to a state society. Vedas refer to society that is very much tribal.

 

[Brahman]

You're not serious with this statement, the gathas are basically diss track on the Devas and vendidad basically contains yo Mama jokes on the Devas. Vendiad literally translates to "given against the Devas" meaning knowledge of the remedies against the Devas.
Yeah the Vedas make no mention of the ahuras or Asuras as being evil things that role is taken by Danava who are a category of Asura, it's only post Vedic that rakshasa and Asura becomes synonyms of although a scholar would know the difference. In rig Veda, indra Agni etc are all called as Ahuras or Asuras.

Besides Vedas and avesta represent Iranian/Aryans at two very different points in time, in their evolution, Vedas were written or rather composed by semi nomadic cattle breeders who came to India while avesta was written again rather composed by settled iranic people or atleast in the process of transitioning from a nomadic life to a settled one and a transition from a tribal to a state society. Vedas refer to society that is very much tribal.

Read what I said, If the split does not happen then they would be considered the same

 

[prani]

Read what I said, If the split does not happen then they would be considered the same

What?, like for the split not to take place, you would have butterflied away the Vedas completely. The Devas referred to in the Avesta are not the Devas of the Vedas, although they refer to by the same name but they are different concepts, they represent the Devas of Iranian Polytheism not the Devas of Vedic Hinduism. Meaning there isn't the so Called Split but rather drift, a drift of history, a drift of culture, a drift of Geography and this drift was caused by migration. In the absence of this drift you would not have a Veda to speak of because the Vedas are a product of Indo Aryans mixing their religious belief with the Cultures in the Periphery of south Asia and the remnants of the Indus Valley Civilization in the North west of South Asia. And it is this Veda that Op is asking about not the Veda that might have been written in say Balkh or Sogdiana or Merv or Khwarazmia or any place mentioned in the Avesta. Like you said Vedas were born in South Asia.

If the Vedic people remain the Southern Central Asia they would have developed a Veda that we could not recognize and it may probably not even be called as the Vedas. Even In that case what you're not saying makes sense, both the Vedas and Avesta cannot be considered as same because at it's root they are from two different religious tradition from probably different tribes that migrated at different times. What you're suggesting is a existence of a Indo Iranian civilization on the banks of of Amu Darya and Syr Darya and later on Helmand, where the Vedic Aryans and the Avestan Mazda worshippers lived in close proximity and later on split and develop hostile relations with each others religious belief and later on as the land dried up and became prone to invasion migrated away to Iran and South Asia.

Edit: Tbh I kinda like the Idea Indo-Iranian Civilization, which would probably existed from 2100 BCE to 1100 BCE, covering the areas south of Syr Darya till the Hindu Kush

 

[manitobot]

When did the Hindu synthesis emerge? How long after the Steppe pastoralist migration was it?

 

[tex mex]

The populations would probably have to be close together though, so you'd probably still need an outpost of this culture somewhere off the Indian subcontinent (that seems to be OP's criterion).

@prani @Madhukar_Shah @Brahman

Zhangzhung - Wikipedia

en.wikipedia.org

I wonder if a Vedic Tribe settled where the Zhangzhung were OTL, and established a kingdom that practiced Vedic religion. ITTL, Vedic religion would spread throughout Tibetan Plateau instead of Bon in OTL.

The Indus and Ganges both lead right back into the Himalayas and Hindu Kush; as an alternative to mountain travel, the Brahmaputra at least deposits you out into the ocean-- so maybe there needs to be some precocious development out in the Bengal area, and then further developments in Arakan. Maybe the timetable for adoption of rice plays into all this somehow

The Bengal Delta was quite underdeveloped with Mangrove Swamps, and Bengal east of Ganges river was isolated and underdeveloped. It had very little to do with Rice adoption, but rather due to shifting course of Ganges river and cultural constraints. The river kept shifting east ward, and a delta was builtup. Not only that, the Vedic peoples were hesitant to migrate into foreign lands due to fear of losing purity, and this resulted in Bengal remaining relatively underdeveloped until the Medieval era, despite the Pundra and Vanga tribes existing in Bengal early on and Buddhists, Jains and Ajivikas having a very early presence in Bengal. Arakan was even more so, and Arakan itself became overcome with Burmese settlement in the tenth century AD.

Somehow, a Vedic tribe must settle in Eastern Bengal and Arakan by the 9th century BC. Could the Vedic Tribes even settle in Burma?

Wait a minute-- isn't this nearly what the Mitanni did out in the Near East, depositing an equestrian elite that expressed its prayers to "Indar"? I suppose it's not Vedic in the sense of operating on the scriptures as we know them, but something of its like has happened before.

The Mitanni elite originated from mercenaries employed by the Kingdom of Mari in Syria around 1750 BC. These Indo-Aryans were employed as mercenaries, not as a conquering wave. Centuries later, these Indo-Aryan Mercenaries seized power and established the Mitanni kingdom. The result was that they were largely assimilated into the local cultural milieu with the exception of some cultural elements. For example, they used Hurrian language and patronized Hurrian deities. Though there was some Indo-Aryan terms, names and deities.

So in that sense the "Atenist" thing would be to defy this abstraction and whatever philosophical edifices may be built on it. In other words, take away the Upanishads' interpretations, from which we derive the whole metaphysical vocabulary that later Hinduism uses, and what you're left with is... meat for the Fire God.

Good insight.

 

[prani]

The Bengal Delta was quite underdeveloped with Mangrove Swamps, and Bengal east of Ganges river was isolated and underdeveloped. It had very little to do with Rice adoption, but rather due to shifting course of Ganges river and cultural constraints. The river kept shifting east ward, and a delta was builtup. Not only that, the Vedic peoples were hesitant to migrate into foreign lands due to fear of losing purity, and this resulted in Bengal remaining relatively underdeveloped until the Medieval era, despite the Pundra and Vanga tribes existing in Bengal early on and Buddhists, Jains and Ajivikas having a very early presence in Bengal. Arakan was even more so, and Arakan itself became overcome with Burmese settlement in the tenth century AD.

Unpopular method but they could raid and enslaved the people in Bengal and north eastern parts establish rice and sugar plantation and force the native to adopt the Vedic faith

 

[tex mex]

Unpopular method but they could raid and enslaved the people in Bengal and north eastern parts establish rice and sugar plantation and force the native to adopt the Vedic faith

I don't think this is necessary at all.
The Sinhalese arose when a migration of Vanga kingdom in West Bengal to Ceylon occurred. Before Buddhism, the Early Sinhalese practiced Vedic religion as seen with purohit Upatissa nuwara. The Pre-Buddhist Dhivehis of Maldives practiced Vedic religion, and the ruling dynasty(Addatee) claimed Suryavamsa lineage.

I am thinking a maritime migration from either Kalinga or Vanga kingdom as these kingdoms had Vedic religion. The migration can be to Southern Burma, with Burma becoming gradually Indo-Aryan.
Another possibility is a migration from Gujarat or Sindh to Oman. I can see Oman becoming a collection of indo-aryan tribes that practice Vedic religion. They can then propagate this amongst the Arab tribes.

 

[prani]

on't think this is necessary at all.
The Sinhalese arose when a migration of Vanga kingdom in West Bengal to Ceylon occurred. Before Buddhism, the Early Sinhalese practiced Vedic religion as seen with purohit Upatissa nuwara. The Pre-Buddhist Dhivehis of Maldives practiced Vedic religion, and the ruling dynasty(Addatee) claimed Suryavamsa lineage

Look i may be geographical determinist but you're not going to have a bunch of people from the north west of south Asia who are used to dry and hot climate to migrate into the the tropical regions, which is why indo Aryan migration stopped put to North west and central south Asia, it's only after some half a millennium did they migrate further south after acclimated to the tropics. By then Vedic would probably have went into a decline.

The issue here seems to me is that, Vedic faith losing its popularity as the society evolved. Maybe for Vedic faith to remain relevant as society evolved in complexity is to codify it and become reactionary?.

 

[LostInNewDelhi]

Since all the answers here amount to "what if this society was completely different-- in geography, staple foods, really anything except religion": why not just bite the bullet and bring in writing? Can we credit the persistence in Egyptian or Mesopotamian ideology, or key concepts set as constants within an overall flux, to being able to write down a specific version or depict it in art? Stuff like the Pharaonic lore especially-- the way we can see artistic motifs like "king smacks his enemies with a flail" across thousands of years. Or the way that Mesopotamian civilization could preserve several millenia-old dead languages-- Sumerian, Akkadian, and so on-- and let the ideas in them become a kind of unchanging yardstick for their achievements.

So, whatever-- instead of Brahmi scripts coming out of wherever they came out (likely evolving like Ge'ez did, a syllabary built out of Semitic consonantal characters), have them being upstaged by some even earlier hieroglyphic system. As for the medium-- clay tablets and masonwork are great, tree bark or cloth. Great stone tablets declaring that so-and-so was a great performer or sacrifices, so if you want to measure up you know what to do.

Don't think we need any Indus Valley Civilization connection, play around with any set of symbols long enough and you'll make a system that works, if one isn't already introduced from abroad by then. Item labels make up inventories of nouns and numbers (and maybe adjectives and verbs), fortune telling devices begin to develop a vocabulary and syntax of mundane and otherworldly affairs.

 

[tex mex]

Look i may be geographical determinist but you're not going to have a bunch of people from the north west of south Asia who are used to dry and hot climate to migrate into the the tropical regions, which is why indo Aryan migration stopped put to North west and central south Asia, it's only after some half a millennium did they migrate further south after acclimated to the tropics. By then Vedic would probably have went into a decline.

I don't think its the climate.
The tropics are very desirable, as they are very rich in terms of fertility. The issue was that the Aryans settled very quickly in the Ganga Yamuna Doab and became less motile. As such, expansion into Awadh and Bihar regions took more than 500 years as you said, while Aryans were already reached Vindhyas. This was because of less motility due to increased settlement and development.

The issue here seems to me is that, Vedic faith losing its popularity as the society evolved. Maybe for Vedic faith to remain relevant as society evolved in complexity is to codify it and become reactionary?.

Vedic religion was codified as Srauta.
Vedic culture spread as far as Ceylon and Maldives, but was supplanted by buddhism. Kerala still has some of the Srauta practice remaining, but did not want to propagate back to Maldives and Sri Lanka after buddhist conversion.
The reactionary mentality restricted its spread. If you cross a river, they say you will become impure. If you go to barbaric land, you become impure. Vedic religion could have spread as far as Burma and Tibet, but the Vedic Priesthoods were against missionary work in these regions as they were considered barbaric.
The best way is for migration, like with Ceylon and Maldives. You need to have Indo-Aryans migrate into Burma and Tibet. These tribes develop into kingdoms and adopt Vedic rites.
Indo-Aryans migrate to Southern Burma by ship around 600 BC from West Bengal or Kalinga.
For Tibet, some Dardic tribe settles around mt.kailash by following indus river. They establish a kingdom with Vedic rites in western tibet.

 

[prani]

The reactionary mentality restricted its spread. If you cross a river, they say you will become impure. If you go to barbaric land, you become impure.

The Kala Pani practise that you're talking about it post vedic and belongs to the Dharma Sutra era when laws were being codified. The Vedic Age is the time period that begins with the Migration of the Bharatha and the Puru tribe into what is now Pakistan Punjab and later on it's merger to form the Kuru Clan and its rise and includes the Kuru Kingdom/clan establishing itself in the Doab and imposes it's hegemony through out north western India barring Rajasthan and Sindh and includes the time when the Kuru Kingdom was the most powerful, that is from 1200-800 BCE and ends gradually with the Shift eastwards into the Ganges which also coincides with the defeat of the Kuru Kingdom by the Non-Vedic but Indo Aryan Salva Tribe. This period of 700 years from 1500 BCE to 800 BCE is the Vedic age. The Kuru Kingdom marks the Maturity of the vedic and it's decline marks the end of the Vedic age. The Yajur, Sama and the Atharvaveda were composed in the Kuru Kingdom as is evidenced by the frequent reference to the Kuru Clan, whereas the Rigveda refers to the period prior to the merger of the tribes, which is why you find a lot of contradictions in the Rigveda and less so in other vedas because Rig Veda is in essence represents the Hymns belonging to different tribes.

So when i Said reactionary, it's reactionary to this time period not the following time period. The Kala Pani, is probably Alien to the Vedic people since they basically went from being of the Periphery of the Subcontinent to the banks of Ganga and Yamuna River in a matter of Just 500 years and in that time period they went from being nomads to a settled people.

Vedic religion was codified as Srauta

I think you're getting confused, Srauta Sutras, which is part of the Kalpa which is one of the Vedanga was composed in 600 BCE, so they were composed towards the end of the Vedic age after that came Shulab Sutra, this was composed somewhere around the same time as the Srauta or somehwat later as the two are related, some 300 Years later came the Samrta Sutra and finally we have the Dharma Sutra from which the Dharma Shastras emerge.

Vedas was the Codified Vedic religion while the Srauta was based off Veda composed somewhere in the middle of the First millennium BCE so it's post Vedic and if you're very liberal with time periods you can classified it as Late Vedic, but certainly does not belong to the Vedic age. You can it is based off Vedic tradition and is very closely linked to it but saying that it is the Codified Vedic religion is a bit too far. In fact the Srauta marks the end of the Vedic age, when the old hymns were collected and new rituals were introduced.

The tropics are very desirable, as they are very rich in terms of fertility

Also rich in malaria and host of other diseases, at the time of India's independence about 25 percent of the people had contracted Malaria at some point in their life and lot were dying from the disease. May be if we see it from their point of view of people dying because of fever, they probably though that land was cursed. Yes even north west of South Asia have incidence of malaria BUT is far less when compared to the Central and eastern parts of the subcontinent and this is because of dust storms and heat waves that kill most of the disease causing germs.

The issue was that the Aryans settled very quickly in the Ganga Yamuna Doab and became less motile. As such, expansion into Awadh and Bihar regions took more than 500 years as you said, while Aryans were already reached Vindhyas. This was because of less motility due to increased settlement and development.

I don't see it as a bad thing, a society can develop extensively or intensively. The middle and Late vedic period marks the intensive development Phase of the culture, the painted grey ware culture is basically the Kuru kingdom, so far over 1700 sites have been discovered and from what i Spoke with the archeologist, there must be over 10,000 settlements belonging to that era situated along the the streams of the Doab, Ganga and Yamuna. You had farmers developing techniques such as double cropping, multi cropping and other innovations in agriculture together with the widespread use of the plough and other Iron tools that enabled the clearing of the forest and all of the contributed to the creation of massive surplus that supported the cities.
The early Vedic period on the other hand marks the extensive development phase where new people were absorbed, new lands explored and this is as you said because people in the early Vedic age were semi nomads.
For Rapid expansion of the Vedic people and consequently their culture, might i suggest
1. The right of Primogeniture, the eldest male child gets the property and the younger ones gets nothing, this will act as a push factor, forcing the men to migrate.
2. Make monogamy the norm, this is so that the women follow the men into the new lands and not end up marrying a man in the territory that their family is familiar with. This is another Push factor
3. Make the society more unequal, have most of the land owned by a few elite men. This is sorta a pull-push factor, people in already settled lands would seek out better prospects because of the poor living conditions and the new lands would act as a pull factor, a chance to start a new life.
4. Have the Kuru State survive longer and develop expansionist policies to ease the problems associated with population increase. This is because the Kuru State is the Vedic society, it was under it's hegemony that Vedas were developed.

Vedic Priesthoods were against missionary work in these regions as they were considered barbaric.

You do realize this is quite normal for religions back in those days, there is nothing special about the objections of the Vedic Priesthood. Religion was associated with one's tribe and you subjugate another tribe. If you do "Missionary" work, it basically means the other tribe is equal to your tribe and hence cannot be subjugated and tribute cannot be extracted or special privileges to the conqueror maintained . This is the same reason why the Umayyads had objections with conversion. If your non muslim subjects can no longer be taxed then you can no longer Jiziya.
Now Zoroastrianism is kinda an exception to this rule, all you have to do is accept the teaching of Zarathustra Spitamaha and you're a Mazda Yasni and this did not prevent the Persians from imposing tribute to their fellow Zoroastrian kingdoms that they conquered but you need a change in Ideology of what a religion means.