Exhibition
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Oxford University Museum of Natural History
Until 24 February 2020
IT CAME to be known as Darwin’s dilemma: why did animal life appear abruptly in the fossil record 542 million years ago, having left no trace in earlier rocks? In his book On the Origin of Species, Charles Darwin admitted: “I can give no satisfactory answer.” The origin of animals was duly elevated to one of the great mysteries of evolution.
In the past few decades, the mystery has been solved. Animals didn’t appear in the blink of an eye during the “Cambrian explosion”, but evolved gradually in the Precambrian, the so-called “long fuse” of the Cambrian explosion. Even so, the origin of animal life remains one of palaeontology’s most interesting and contentious questions, and the fossils telling the story are among the world’s most famous and fascinating.
Many of the best are on display in a small, rather beautiful exhibition called First Animals at the Oxford Museum of Natural History. It is a rare, possibly unique, chance to see specimens from the world’s three most important Cambrian explosion fossil sites side-by-side. For anyone fascinated by that time and its amazing cast, it is a must-see.
The stars of the show are 55 fossils from the Chengjiang deposit in China, a site that since its discovery in 1984 has surpassed the better-known Burgess Shale in Canada in scientific importance. The fossils are exceptionally well preserved, like those found in the Burgess Shale, but at 518 million years old they are 10 million years older, putting them right in the thick of the evolutionary action. The Burgess Shale, in contrast, represents the calm after the storm, once the full range of modern animal groups had evolved.
Many of the Chengjiang fossils have never been seen outside China before. “It was like Christmas,” says museum palaeontologist Duncan Murdoch, recalling opening the box when it arrived on loan from Yunnan University in China.
Burgess Shale fossils are also on show, plus some from a lesser-known but equally important site in Greenland called Sirius Passet. Then there are casts of Ediacaran fossils, representatives of an ecosystem of large animals that lived long before the Cambrian. “I think this is the first time material representing so many different stages of animal evolution has been brought together,” says Imran Rahman, a research fellow at the museum.
The science providing the show’s context is explained well, tackling arcane material such as molecular clocks and developmental genetics, though there is no mention of the Doushantuo deposit, also in China, which some palaeontologists say preserves the very earliest animals. For kids small and big, there is an interactive exhibit allowing you to explore the Cambrian ocean in a submersible.
This is a brave exhibition to stage. Compared with, say, feathered dinosaurs or extinct marine reptiles, the fossils are small and relatively uncharismatic. The nearest thing to a mega-beast is Amplectobelua, the top predator in the Chengjiang ecosystem, which cruised above the sea floor and shredded prey with its vicious spiny claws. It was as big and fierce as anything in the ocean at the time, yet still only about the size of a living langoustine.
But as Murdoch says, good things come in little packages. The extraordinary detail of preservation seen in some of the fossils is a thing of wonder. These animals are more than half a billion years old yet their eyes, gills, legs, internal organs and even muscles are intact. For a glimpse of life right at the start of the age of animals, you can’t ask for anything better than this.
Hear Alice Roberts describe the
