No doubt, the place of origin of Hinduism is in India as evidenced by many excavation sites and historical documents but it is hard to pinpoint the year when did Hinduism start. The origin of other religions like Islam, Christianity, Buddhism, etc. is easy to trace because of the knowledge about the birth dates of their founders.
The main reasons behind difficulty finding the exact year of origin of Hinduism are as follows:
1. Hinduism was not founded as a religion. It was just a way of life or culture you can say at most but later on, the people following this culture were called Hindus, and their culture was termed as Hinduism.
2. The second thing is that there is no single founder of Hinduism as there is for other religions.
Because of the above-mentioned two points, it is very hard to pinpoint when did Hinduism start, but still, we can find out an approximate period when some of the practices of Hindus began.
Origin of Hinduism Based on Available Historical Pieces of Evidence:
Though modern Hinduism is largely based on Vedas, Hindus still practice some traditions which resemble the Neolithic people of India. According to historians, Neolithic age lasted till about 4000 B.C. This age existed roughly between 10000-4000 B.C. Neolithic people were more cultured than Paleolithic or Mesolithic people. The practices like cremation and burying the dead body were common. The other common practices between Neolithic and modern Hindus are ancestral worship, stone worship, phallus worship, animal sacrifice, etc. Hindus worship idols and pray to their ancestors on some particular days of the year. The phallus worship resembles Shiv Linga worship. Animal sacrifice is still a part of some Hindu rituals. The history of some tribes of India is believed to be as old as the Neolithic era.
By looking at the above points, we can easily conclude that Hinduism did have its traces to the Neolithic culture of India. Hence, Hinduism must have originated between 4000 B.C. and 10000 B.C. in India.
More articles related to Origin of Hinduism:
History of Hinduism Founder of Hinduism
Hinduism as Hinduism is based off the Vedas, any influence from older sources is noteworthy, but Hinduism started with the people whom the Vedas were about. And to include things that strongly go against the actual teachings (like animal sacrifice, that had old roots that predate anything that resembles modern, or even the ancient yet structured, religions) makes me think you are an atheist who is intentionally dismissive of religious beliefs/practices/teachings.