The most striking feature of monotremes is that they are egg-laying mammals, but this was only accepted by the scientific establishment eight decades after specimens of echidna and platypus were first examined in Europe. Even before the specimens were sent, colonists had been told by Indigenous Australians that the echidna and platypus laid eggs. In this paper I briefly summarise aspects of the significance of monotremes in some mainland Aboriginal cultures, and the attempts by the naturalist George Bennett to discover if platypuses were oviparous. In Tasmania the disruption of Aboriginal culture early in the 19th century meant that there are very few details known of their insights into ecosystems and monotreme biology. Some incidental information was recorded by George Augustus Robinson during his “Friendly Mission”, while what appears to be a previously unremarked presentation at the Royal Society of Van Diemen’s Land in 1849 reveals Aboriginal knowledge of the reproductive behaviour and life history of Tasmanian echidnas not described in the scientific literature until very recently.