Small-scale irrigation agriculture becomes more common and lessens the dependence on marine resources for food. Larger and more stable populations result. The making and firing of ceramics throughout expanded areas of northern South America appear to coincide with the increase in food supply. The north central regions of Peru, both highland and coast, experience prosperity and settlements grow to include impressively sized public structures. The use and availability of luxury objects such as seashells, rare and colorful bird feathers, and semiprecious stones, indicate a growing status differentiation in social class.