The delta and surrounding hills has been inhabited for hundreds of generations (thousands of years). The area supported agriculture very early on. About 500 BC there was a shift to growing rice. This led to the development of urban areas. Because there were no stone quarries in the area houses were built of wood and mud (including adobe). Because of the monsoon climate very little evidence of the earliest inhabitants remains. From about 300 BC to the 1700s AD the Bengal delta saw the development of writing, the Bengali language, religions and the rise and fall of states. By the 1500s, the area was prosperous and even peasants had plenty to eat.