The monotremes belong to an ancient order of mammals represented by only five living species – the duckbilled platypus and four species of echidna (or spiny anteater). All of these mammals have several things in common. They are endemic to Australia, have some primitive skeletal features, and lay eggs. Today we recognize this order as being one of the three orders of mammals, along with marsupials and placental mammals, but it was not always this way in the past.
Until the time that Europeans first encountered platypuses and echidnas in the 1790s, it was assumed that all mammals give birth to live young. The proposal that some mammals reproduce by laying eggs was considered preposterous in early 19th century zoological circles. But then, the subject became the topic of great debate and naturalists were encouraged to find evidence of these egg-laying mammals.
“In the nineteenth century, many conservative scientists didn’t want to believe that an egg-laying mammal could exist, because this would support the theory of evolution – the idea that one animal group was capable of changing into another,” said Jack Ashby, assistant director at the University of Cambridge Museum of Zoology.
“Lizards and frogs lay eggs, so the idea of a mammal laying eggs was dismissed by many people – I think they felt it was degrading to be related to animals that they considered ‘lower life forms.’”
For 85 years, European naturalists attempted to find proof that platypuses and echidnas lay eggs. They sought the help of Aboriginal Australians and sent reports home to Europe – all their results were either ignored or dismissed as fantastical. However, in 1883, William Caldwell, a Scottish zoologist working at Cambridge University went to Australia to resolve the burning question.
Caldwell set up camp on the banks of the Burnett River in northern Queensland and began hunting for platypus and echidna specimens and eggs. After extensive searching, and assisted by a team of 150 Aborigines, he collected around 1,400 specimens to be sent back to Cambridge. In 1884, the team eventually found an echidna with an egg in her pouch and a platypus with one egg in her nest and another in her body, just about to be laid.
Caldwell sent news of his triumphant findings back to his mentor at the university. Monotremes were indeed oviparous! The confirmation spread around the world, as though the colonial scientific establishment could now believe this evidence because it had been confirmed by “one of their own.”
While doing recent research on a book about Australian mammals, Ashby began to wonder what had happened to those original specimens collected by Caldwell during his fact-finding mission in Australia. He considered it most likely that they had been brought to the University Museum but there was no record of them in the Museum’s catalogue. He asked Collections Manager Mathew Lowe to look out for specimens that would fit the description and, three months later, was rewarded with a box of jars, each one containing a tiny platypus or echidna specimen.
“I knew from experience that there isn’t a natural history collection on Earth that actually has a comprehensive catalogue of everything in it, and I suspected that Caldwell’s specimens really ought to be here,” explained Ashby, who was delighted at this exciting find.
“It’s one thing to read the 19th century announcements that platypuses and echidnas actually lay eggs. But to have the physical specimens here, tying us back to that discovery almost 150 years ago, is pretty amazing.”
At the time of their collection, these specimens were key to proving that some mammals lay eggs – a fact that changed the course of scientific thinking and supported the theory of evolution. But the unique assemblage of jars had not been catalogued by the Museum so, until recently, staff had been unaware of its existence.
The newly discovered collection includes echidnas, platypuses and marsupials at varying life stages, from fertilized egg to adolescence. Caldwell was the first to make complete collections of every life stage of these species – although not all of the 1,400 specimens have been found in the Museum. Details of the specimens that have recently been rediscovered among the Museum’s collections are published today in the
Ashby says that over the last two centuries, scientists have consistently belittled Australian mammals by describing them as strange and inferior. He believes that this language continues to affect how we describe them today, and undermines efforts to conserve them.
“Platypuses and echidnas are not weird, primitive animals – as many historic accounts depict them – they are as evolved as anything else. It’s just that they’ve never stopped laying eggs,” he said. “I think they’re absolutely amazing and definitely worth valuing.”
The quill-covered echidnas are the most widespread mammal in Australia. They inhabit different ecosystems over the whole continent and have adapted to live in all climates, from snow-covered mountains to the driest deserts.
Platypuses are unique among mammals in that they can detect electricity, and can produce venom. With a tail like a beaver, a flat bill, and webbed feet like a duck, the first specimens brought to Europe were considered to be fakes that had been sewn together.
Ashby’s new book, Platypus Matters: The Extraordinary Story of Australian Mammals, was published in the UK on May, 12 2022 by HarperCollins.