In the past, people threw out their rubbish in particular sites much as we do today. These sites are called middens and are the archaeological treasure troves of how people used to live.
Middens can contain food remains such as shellfish shells, animal bones, ash from fires, broken tools and household objects. The rubbish left behind by people long gone gives us an insight into what people ate and how they lived. In New Zealand, a midden is the most common archaeological site.
What does a midden look like?
Most middens in New Zealand are found along the coast and contain high numbers of shells in layers with bone and ash. They may also contain shards of stone from making tools and bone fishhooks. Middens usually look like a low mound and are often found eroding from sand dunes, river banks or road cuttings. The presence of charcoal, burnt stone or blackened soil tells us that it is from human origin rather than just a natural accumulation of shells.
Middens in New Zealand from early European settlements are similar to ancient Māori middens but often contain bones from domesticated animals such as sheep, cattle and pigs. They may also have pieces of glass or crockery.
How do we know how old the midden is?
If archaeologists are able to recover charcoal, bones or shells, they are able to use radiocarbon dating techniques to estimate the age of the material in the midden. Radiocarbon dating is only possible on material that has once been alive, so it is not possible to date any stone tools or shards.
The story middens can tell
Studying the contents of middens can show where people went to get their food, what proportions of different foods made up their diet and how it may have changed in different seasons or over long periods of time. For example, the study of middens in southern New Zealand has shown that early Māori first concentrated their hunting on moa and seals, which were rich in protein and fat, but later on, as these resources became scarce, they turned to fish and shellfish, supplemented by muttonbirds and weka to maintain their diet
It is from studying midden sites that we know about bird species that have become extinct, such as the moa, the Haast eagle and swans. Studies have also shown that some species were once abundant in areas where they are now rare. For example, elephant seals and fur seals had breeding colonies as far north as the Coromandel Peninsula 700 years ago, whereas now these are confined to the far south. Seeds, pollen and charcoal can also tell us about the plant patterns from the past.