Some historians say that Hinduism had its roots over 5,000 years ago in a wave of migration that brought a pale-skinned, Aryan people down from the northwest into the Indus Valley, now located mainly in Pakistan and India. From there they spread into the Ganges River plains and across India. Some experts say that the religious ideas of the migrants were similar to ancient Iranian ( devas and asuras)One thread common to many cultures and also found in Hinduism is a flood legend.By a process of inter mingling with all the philosophies that includes vedic, non vedic, indigenous folk religion of the time and region. Hinduism was formed.
Tribes who were present in India before arrival of proto Vedic tribes:
Before arrival of protoVedic tribes, there were mainly three major groups.
(*proto Vedic: period that was before classical Vedas,Vedas and Vedic people in its classical form resulted after assimilating Indian sub continents thoughts and people respectively)
(Meena tribes of north India, Matsya or Machcha kingdom of vedic age, pandiyas of south are their **cultural descendents)
(Bhils of north India, illavars of srilanka, cheras, munda dravida tamils, Billavas of Tulunadu of Karnataka, izhavars of kerala are their cultural descendents)
(Pockets of people spread over Nepal , bunts, Naga people of Sri Lanka, north eastern countries, nairs of kerala , nagavanshi of north India, naidus of Andhra etc are their cultural descendents),
Also look Book: The Tamils Eighteen Hundred Years Ago By V. Kanakasabhai
Meenavars and Villavars were allies and spread south of Iran and Afghanistan in prehistoric times. [There are still pockets of Dravidian speaking groups in these areas. (Brahui)]
After that Naga tribes came. Villavars and Meenavars were fighting against (or not considered friendly) Nagas; but were gradually pushed to the southern parts of peninsula. This was achieved by Nagas with the help of new tribes called protoVedic tribes popularly known as Aryans. (Migrated from Russia, andranova, -Iran to India.)
After the arrival of proto Vedic tribes:
ProtoVedic people mixed with local population assimilating their culture and people. But, retained their proto Vedic background; notably, the importance given to priesthood. They can be called as Vedic tribes
Relation between Nagas and Vedic tribes were mixed in the sense if they were allies or not. As at some point of time they were allies like at the time of hostility between Meenavars and Villavars. But some time both Nagas and Vedic tribes were hostile.
Indraprasta ( capital city o pandavas) was made after displacing Naga people who was inhabited there before. They might have been trying to regain their territory from Vedic people, as we can read from Mahabharata that Parikshit is killed by a Naga warrior Takshaka who came to his court in disguise.
(Alliance between Nagas and yaadavas:
To protect Krishna from Kamsa; Vasudeva, with the help of chief of Naga warriors named Ananta, took Krishna to Vrindaavan.)
Tribes who were present in India before Meenavars, Villavar and Nagas.
This of migration process might have happened before, as there was other indigenous tribe who were present before Meenavars Villavar groups, probably Australoid people, can be present 'tribes' of Orrisa, Bengal, kerala etc. (though cannot be tell for sure, and as mixing of population had occurred).
But the Andaman tribes are considered the oldest tribes who came to India even before the Australoid people.
Some of the proofs of this can be seen from below:
Santals tribes of Orrisa believed in a religion called santhal. They believe in the supreme deity, who ultimately controls the entire universe (Thakurji). And the most important spirit is Maran Buru (Great Mountain) is that mount Meru of Africa?
Different path of Evolution of people, culture, language, script:
Evolution of people, culture, language, script, will not be in same path. Tamil language and script are evolved from different source. (Modern Tamil language from proto Dravidian, script from brahmi belonged to Phoenicians)
Like that cultural descendant may or may not be genetical descendant.
Some time culture goes away, people, language stays. Some time language stays in a region, but people, culture, script migrates away.
For example the people of Brahui in Pakistan and Afghanistan speak a Dravidian language. The people (with exceptions) are not Dravidian people, but the area belonged to the Dravidian speaking people in prehistoric time
Examples for that can be seen in present time. For example people of South Africa now speak non native English language which is foreign and was not evolved with them.
Contrary to that Konkani people of kerala though foreign, speak native Malayalam
Process of pushing:
This process of "pushing" of one tribe from their native lands was not swift. As we can see the culture, language and people of proto Vedic tribes and the other tribes migrated to India before them mixed so well that is difficult to distinguish.
(For example: Mother of Vyaasa, Satyavati belonged to matsya kingdom. The Matsya tribes who were there before proto Vedic people)
Take Sanskrit the Retroflex phonemes (as in peet'ham, or mangalam is not common in indo-Iranian languages like Avesta (close cousin of proto Sanskrit). Also words like 'iti', kumāra in Sanskrit, which show the influence of Dravidian language on Sanskrit
Genetical studies also show thorough mixing of these people over centuries so that it is unable to differentiate
Take the beliefs proto Vedic people gave more prominence to devas and asuras. Siva and kali was a god of prehistoric India and Indus valley people, naagaaradhana was predominant among Naga people. But later trimoortis got more importance and devas became semi gods.
It is to be noted that the 'first' avatar of Vishnu occurred in south India or among Dravidian tribes (in fact the story of matsya purana is same as story of Noah's ark in bible. the story belonged to whole human tribes in the form of Deluge myth)
But all were revered irrespective of cultural back ground. All these show that, they have been together for a long time. This may be due to the fact that in early times there was no reluctance among cultures to mix.
We can still see this phenomenon in Nepal, were Hinduism and Buddhism is not separated in to two groups.
There were many people with name 'Krishna- "the black one" in Mahabharata, Ramayana and puranas suggesting that the Vedic people had lived along with indigenous population in harmony. Some prominent ones with name that indicate their colour as you know are Vaasuseva Krishna, Draupati (also Krishnaa), Vyaasa (Krishna Dvaipayana), Ishvara Krishna ( samkya philosopher)
Caste system in India.
Different groups or tribes came to a place at different intervals under the influence of caste system labeled as different castes. One interesting pattern is that the one who came last would become higher caste.
For example izhawars of kerala were actually come from three sources.
One group was Muda Dravidian Tamils. Second one was the Buddhist people who came from Magadha during the period of emperor Ashoka and his successors. The other was Sinhala warriors who came to help chera kings, who were also the Villavar tribes (Izhawars). The community had farmers, physicians (vaidyars) warriors (kalari), rulers (chera rulers) and priests.
But as the Naga people came and defeated Villavars, power shifted to Nagas. The titles of Cheraman were then awarded to Nagas (which were the title given to Villavar rulers earlier.).
Things again changed when Brahmins came to kerala, society got divided in to caste system.
But many prominent families of Nagas and Villavars were absorbed or converted in to Brahmin class and class Kshatriya (also in the reverse order) at early stages of migration. But later caste system became strong and the divide became clear and unable to cross over as it happened in other parts of India.
(See other example, Bhils of north India is considered as Kshatriya were izhawars of south as lower class though belonging to same stock.)
Thus to some extend caste system is the preservation of groups migrated to a place at different times.
Traditions other than Vedic tradition:
Hinduism in its present form is rooted on 10 philosophical schools and 2 unorganized philosophies namely
"consciousness, in an evolving primordial Matter, trying to achieve a higher equilibrium(satva) defying inertia ( tamas) by using active forces ( rajas)"
A school emphasizing meditation closely based on Samkya ( in later stages) It concerned principally with the cultivation of the mind using meditation (dhyana) to further one's acquaintance with reality and finally achieve liberation.
3.Nyaya school or logics
It believed that obtaining valid knowledge was the only way to obtain release from suffering
school of atomism says universe is build by minute particles which is being controlled by universal consciousness
5.Mimamsa school, Emphasised on the ritualistic vedic tradition
6.Vedanta school, Emphasised on the philosophical vedic teachings, notabily monoism and non duality, the goal of Vedanta is a state of self-realization or cosmic consciousness
7.Buddhist school: (Shramana school) Emphasis on karma, liberation from suffering, Noble Eightfold Path and middle way.
8.Jainist school: (Shramana school) Every living soul as potentially divine. When the soul sheds its karmic bonds completely, it attains divine consciousness. It prescribes a path of non-violence to progress the soul to this ultimate goal.
9.Cārvāka school: Not believed in those which cannot be perceived.
10.Ajivaka school : believes in fate, which dictates one's life.
11(Folk Hindu).Nature worship- saktiyism mother earth goddess, city goddess,snake worship (nagaradhana), mountain gods, kaavu.
12. Ancestor soul worship- (karanavar aatma).believes that a family is protected by ansistors.
All these were both atheistic and theistic (in context of belief in god) at some point or other in history.
Among this the 5 and 6 recognized Vedic authority. First 3 recognized Vedic authority partially (or from some point of time in history.). 7, 8 and 9 don't recognized Vedic authority.
Fusion of above philosophies and beliefs of the other indigenous people like ancestor worships and nature worships resulted in the three main Indian religions in its present form (Hinduism Buddhism and Jainism)
Olden times philosophies of India were broadly classified as Brahmanas ( or Brahmanae by Greeks) (of Vedic tribes) and shramanas or ( Sarmanae by Greeks) (7, 8 &9). Later, by name Smartist (Vedic) and shramanas (non Vedic).
Major characters of Hindu belief:
1. Pre Vedic (folk) - based on local believes
2. Vedic - Based on vedic belief
3. Shramana -based on nonvedic believes.
4. Smartist -based on vedanta,upanishad
5. Puranic- based on stories of puranas, ramayana, mahabharata, bhagavat gita.
6. Karmic -based on karma, duty,yoga etc
7. Bhakti - Based on practice of worship.