Using sedimentary ancient DNA in coastal and marine contexts to explore past human-environmental interactions in Australia.

Over the 65 000 years of human occupation in Australia, sea levels have fluctuated significantly, notably rising from -120 m around 21 000 years ago, submerging vast areas of the continental shelf. Current coastal ecosystems stabilized about 5000 years ago, leaving many early cultural landscapes underwater, complicating the study of ancient human activity. Sedimentary ancient DNA (sedaDNA) analysis, a powerful tool for monitoring ecological changes and human-environment interactions, has recently gained attention but its exploration is still in its early stages in Australia. This approach holds great potential for investigating shifts in resource and land-use changes, the introduction of non-native species and distinguishing between human and natural impacts on biodiversity. Despite challenges with DNA preservation due to Australia's harsh climate, organic-rich coastal and marine sediments may provide favourable conditions for sedaDNA. We review case studies across Australia, showcasing how sedaDNA offers valuable insights into past coastal ecologies and can contribute to developing a sustainable biocultural landscape.This article is part of the theme issue 'Shifting seas: understanding deep-time human impacts on marine ecosystems'.