Rare egg-laying mammals fossils rediscovered

Cambridge University has a famous Museum of Zoology. And like all museums, it’s got a lot of artefacts that have never been properly catalogued, or were packed away years ago and forgotten. And recently, going through some of these “lost finds”, assistant director Jack Ashby came across an amazing piece of history: the collection of platypuses, echidnas and possums - dating back to the 1880s - that convinced the world that these animals were real. Previously people couldn’t believe they weren’t some sort of hoax: “how can a mammal lay eggs?” they protested! The specimens were assembled by William Caldwell who was paid to travel to Australia, from Cambridge, just to answer this question. Those were the days weren’t they! Robert Spencer went to the Museum of Zoology to see these decisive specimens, and find out exactly what Cambridge University, Australian aboriginal people, and the French revolution had to do with it…

Jack - So the smallest ones we've got here are two little tiny echidnas. They're like eight millimeters long and they're they're pink. These are from within an egg. There's a tiny bit of yolk sac there, I think. And so these are the youngest ones in front of us. And at the other end of the scale, we've got a puggle here, which is a baby echidna - that's about 12 centimeters long. It's got no spines. Echnidnas, for those who don't know, are termite-eating, ant-eating egg-laying mammals that are covered in really thick porcupine-like spines. But once they start growing those spines, then they don't stay in the pouch very often. And so this is a pouch young, got a long little snout and really big digging claws for smashing into termite nests.

Robert - I mean, they really do look rather strange don't they?

Jack - Well, that is how they're typically described. So, people describe these animals as strange, as inferior and bizarre and kind of lower life forms.

Robert - Do you think we still have that outlook on them or have they moved from lower life forms to merely curiosities in the modern public eye?

Jack - I think there's probably both. It is quite common surprisingly to see these animals described as primitive, which doesn't make any evolutionary sense - no living species can be considered primitive. Everything is equally evolved.

Robert - What was the European, at least, reaction when these animals were first described?

Jack - So platapus' and echidnas were first described by Europeans in the 1790s and straight away, there was some suggestion that maybe they lay eggs, but that's not something that mamals were supposed to do. So people were very suspicious of it and it took them those 85 years until their actual specimens that they would accept were uncovered.

Robert - Why did it take so long?

Jack - That's a good question. I think a big part of it was that people weren't really willing to accept that mammals could lay eggs, but another defining feature of mammals is that they produce milk. And there was a big question about whether platapus' and echidnas could do that, because they don't have any nipples. This created a big problem because it meant that the rules of how the tree of life had been arranged, didn't work. One scientist on the very much "they do not lay eggs" side of the argument was Richard Owen. He was the first superintendent of the Natural History Museum in London, described countless fossil species, he coined the term dinosaur. But he was also kind of on the wrong side of the Darwinian evolution debate, he was fighting against evolution. But he was the one that proved that they do produce milk. And what he did was get a load of specimens sent over. He looked under the skin and found these glands and squeezed them and tasted the milk that came out, the oily substance that came out

Robert - Do we know what his reaction was?

Jack - He said he couldn't perceive anything other than the taste of the preserving spirits. It just tasted of alcohol.

Robert - So he had specimens, he was examining them, he'd shown that this furred animal was producing milk and still said that no, it couldn't have been laying eggs.

Jack - Yeah, it's bizarre. The problem was basically if you've got an animal that has some mammal-like features and some reptile-like features, then the suggestion is that one group can turn into another one, which isn't quite how we see it today. But basically means that yes, evolution is real. And there's a political side to it too. Owen was a staunch, conservative high-end society and he wanted things to stay that way, I think. The concept that if animals can change over time, should I say, then humans can change over time too. And especially in the decades after the French revolution.

Robert - And science did draw those kinds of parallels at that time?

Jack - Yes. Well, there's a very, very close alignment between who was fighting on the liberal side of political arguments and who was fighting those "animals change" arguments.

Robert - What happened? We're now certain that echidnas and platapus' do lay eggs.

Jack - What happened is, as soon as those species were encountered by Europeans, people were sent to Australia to try and solve the mystery. And indeed settlers in Australia or Aboriginal Australians, were asked whether they could tell them whether they laid eggs. And what you might consider evidence was gathered at the time, like people were saying, "I found this platapus with eggs" or indigenous people were saying, yes, they lay eggs. But that information was ignored or dismissed. So the University of Cambridge and the Royal Society and the UK government sent this recent Cambridge graduate called William Caldwell to Australia with this specific question in mind. They gave quite a lot of money and he employed a massive army of Aboriginal Australians to collect platapus' and echidnas for him. He was trying to find the smoking gun of specimens with an egg in the pouch or an egg in the nest, and that's exactly what he did in August, 1884. He sent a telegram across the oceans to the British society of the advancement of science and shared the news. And given, I think, in that kind of Caldwell was one of their own, they were willing to accept that.