Why was the Indian society tied to the land

Indian society is divided ha1. Brahmins occupying the highest position in India, according to legend came out of his mouth Perosi, the first man2. From the hands of Perosi formed the Kshatriyas, the warriors3. From the thighs of God happened Vaisyas, the peasants and farmers4. As part of the steps were born the Shudra servant.