Given the question: Question: "Why were the two main philosophical schools of the Mahayana in India very similar?"  Context: "During the period of Late Mahayana Buddhism, four major types of thought developed: Madhyamaka, Yogacara, Tathagatagarbha, and Buddhist Logic as the last and most recent. In India, the two main philosophical schools of the Mahayana were the Madhyamaka and the later Yogacara. According to Dan Lusthaus, Madhyamaka and Yogacara have a great deal in common, and the commonality stems from early Buddhism. There were no great Indian teachers associated with tathagatagarbha thought."  Answer:
The answer is:
early Buddhism