While Buddhism was formed as a reaction to the Vedic religion, Hinduism was formed as a reaction to the popularity if Buddhism.  That caused Buddhism to split between mahayana in the north and thervada in the south.  Both religions have evolved along with each other.  Even though they are different religions, they share many similarities, such as non-violence, reincarnation, and the belief that suffering is caused by attachment to physical things.  Buddhism and Hinduism are reactions to each other that allowed for a system of belief for a variety of different people and castes.