The Food and Subsistence of Aboriginal Australians enabled them to adapt completely to their environment. Aboriginal people generally enjoyed a mixed and abundant diet of plant and animal foods that varied according to time of year and local environmental conditions. Their intimate understanding of regional ecology and natural resources enabled some of them to survive in environments that European settlers of Australia still find extremely harsh and uninhabitable.
For the many Aboriginal groups that lived on the coast, fish were an important part of the diet. Some coastal groups built large and complex systems of stone-walled traps that caught fish as the tide dropped. Others used nets of plant fibers to catch fish and, in some areas, eels. In some coastal regions, massive ancient middens (trash heaps) of discarded shells up to 5 m (16 ft) high have been discovered, indicating that certain Aboriginal groups made extensive use of shellfish. Besides eating seafood, coastal dwellers also ate a variety of plant foods and hunted land animals.
For as yet unknown reasons, the inhabitants of Tasmania stopped eating fish about 3,500 years ago, long after the region became separated from the mainland. Some scientists believe the change was related to cultural or religious factors, a decrease in the amounts of fish in waters surrounding the island, or a switch to hunting fat-rich sea mammals and birds. This change may have coincided with an independent development of watercraft by the Tasmanians, who evidently did not have that technology when they became separated from the mainland.
Aboriginal groups in the most arid desert regions relied on a wide variety of lizards for meat and a great variety of seeds, fruits, and tubers. Larger animals such as kangaroos and emus, although prized, were not particularly common in the driest areas. Common plant foods included many kinds of acacia seeds, solanums (a type of wild tomato), an indigenous variety of sweet potato, and the seeds of common grasses.
Many species of large marsupials, birds, and reptiles—or megafauna, the scientific term for these large animals—populated the Sahul landmass when Aboriginal people first arrived there. These included wombat-like creatures the size of rhinoceroses, kangaroos up to 3 m (10 ft) high, huge emu-like birds, giant snakes and lizards, and other large animals. Most of these species became extinct by 20,000 years ago. Given that Aboriginal people arrived in Australia at least 50,000 years ago, Australian megafauna and Aboriginal humans probably coexisted for thousands of years. No evidence has yet been found to show that Aboriginal people ever hunted megafauna, although they apparently scavenged the carcasses of some species. Even so, most archaeologists believe that a combination of human activity and climate changes led to the extinction of megafauna.
About 3,000 years ago, Aboriginal people began to more intensively use a grinding process for a variety of seeds, including wild millet, to make a heavy kind of bread. Among many interior groups, harvesting grain from wild plants became an established practice. However, Aboriginal people never practiced full-fledged horticulture, which involves the deliberate planting of seeds and plants, fertilization, and irrigation. The reasons for this absence of horticulture are unclear. Certainly in the drier regions, where the millets grew, the huge variation in annual rainfall would have ruled it out. In the tropical north, where Aboriginal people at the tip of Cape York were in contact with Torres Strait Islanders who made gardens, the lack of horticulture indicates that people there probably had adequate food resources and low population densities. The Food and Subsistence of Aboriginal Australians was rich in fruits and other agricultural products and for others living close to coastal areas, fish constituted some sort of staple food.