Hinduism is considered to be the oldest religion on Earth because its roots can be traced back to the Indus Valley Civilization, which flourished in the northwestern Indian subcontinent from around 3300 to 1300 BCE. The Vedas, the oldest scriptures of Hinduism, were composed during this period.

There are a number of reasons why Hinduism is considered to be the oldest religion on Earth. First, the Vedas are the oldest scriptures of any major religion. The Vedas are a collection of hymns, mantras, and prayers that were composed over a period of several thousand years. They provide a glimpse into the earliest beliefs and practices of Hinduism.

Second, Hinduism is a very diverse religion. There are many different schools of thought within Hinduism, and each school has its own unique beliefs and practices. However, all of the schools of thought within Hinduism share a common belief in the concept of dharma, which is the universal law that governs all of creation.

Third, Hinduism is a very tolerant religion. It has a long history of accepting and absorbing other religious traditions. This is why Hinduism is often referred to as a "synthesis" of different religious traditions.

Of course, there is no one definitive answer to the question of why Hinduism is considered to be the oldest religion on Earth. However, the evidence suggests that Hinduism has a long and rich history that can be traced back to the Indus Valley Civilization.

Here are some additional reasons why Hinduism is considered to be the oldest religion on Earth:

• The Upanishads, which are some of the most important texts in Hinduism, were composed around 1000 BCE.
• The Bhagavad Gita, which is one of the most popular texts in Hinduism, was composed around 500 BCE.
• The Mahabharata and the Ramayana, which are two of the longest epics in the world, were composed around 400 BCE.
• Hinduism has a rich tradition of art, architecture, and philosophy.
• Hinduism has a large number of followers, with over 1 billion adherents worldwide.

Overall, there is a strong case to be made that Hinduism is the oldest religion on Earth. It has a long and rich history, a diverse set of beliefs and practices, and a large number of followers.