Earth's five mass extinctions
And the start of the sixth?
So far, Earth has experienced five major mass extinctions.
Huge volcanic eruptions, sea-level and climate changes, and massive meteorite strikes have all eliminated whole groups of organisms including trilobites, ammonites, pterosaurs, and all dinosaurs except birds.
In the aftermath of a mass extinction, new species and ecosystems may flourish, but the world will never be quite the same again.
What were the five major mass extinctions?
1. End of the Ordovician Period
Around 440 million years ago
The mass extinction at the end of the Ordovician Period was caused by large-scale glaciation and a global fall in sea levels. Up to 85 per cent of shallow marine species died out, including many trilobites, bryozoans, brachiopods, bivalves, corals and graptolites.
Trilobites and brittle stars
Selenopeltis sp.
2. End of the Devonian Period
Around 370 million years ago
Many marine species were lost in the Devonian mass extinction. Reef-building corals and bony armoured ‘fish’ were particularly hard-hit. Some marine animals, such as crinoids, were not badly affected, though we do not yet know why. Understanding why the mass extinction affected some species more than others is important in assessing today’s biodiversity crisis.
Sea lily
Scyphocrinites elegans
Fossil
3. End of the Permian Period
Around 252 million years ago
Known as the ‘Great Dying’, the biggest mass extinction occurred at the end of the Permian Period. It removed up to 96 per cent of marine species and around 70 per cent of land species. Trilobites, sea scorpions, and rugose and tabulate corals all disappeared forever. The main cause was the global warming that followed large-scale volcanic eruptions.
Rugose coral
Kodonophyllum truncatum
Fossil
4. End of the Triassic Period
Around 201 million years ago
The end of the Triassic Period saw the demise of phytosaurs and many groups of ‘crocodile-like’ archosaurs, which paved the way for the domination of the dinosaurs in the Jurassic and Cretaceous. Conodonts – small but abundant jawless marine vertebrates – were wiped out completely.
Phytosaur
Nicrosaurus kapffi
Cast of fossil
5. End of the Cretaceous Period
Around 66 million years ago
Perhaps the best known of all mass extinctions occurred at the end of the Cretaceous Period. All dinosaurs other than birds disappeared, along with many other large reptile groups, such as pterosaurs, plesiosaurs and mosasaurs. Land plants and herbivorous insects also suffered major losses. The main cause was a huge meteorite impact in what is now Mexico.
Dinosaur
Pachycephalosaurus wyomingensis
Cast of fossil
The next mass extinction?
Human activity has driven extinction rates to hundreds of times higher than the background rate, threatening Earth’s next mass extinction.
Some experts have argued that the sixth mass extinction is already underway. Since the 17th century, extinction rates have accelerated rapidly. Perhaps the greatest threat to biodiversity in the modern era is climate change.
The Bramble Cay Melomys (Melomys rubicola) is the first mammal known to have become extinct due to human-caused global warming. The species was once endemic to a small island in the Torres Strait, north of Australia.
Recorded sightings of the melomys from the 19th century describe the population flourishing. But by the end of the 20th century, alarm bells were ringing. In 2013, it was reported that the melomys' range had been reduced to an area of just 4-5 hectares. As rising sea levels continued to wash away vegetation, the species was left without enough food or shelter to survive, and by 2019 it was declared extinct.
Bramble Cay Melomys (Melomys rubicola)
Bramble Cay Melomys (Melomys rubicola)
3D print of Bramble Cay Melomys skull, courtesy of the Australian Museum
3D print of Bramble Cay Melomys skull, courtesy of the Australian Museum
How can museums help us save species from extinction?
If we are to have any hope of tackling human-caused extinction, we first need to understand it. What causes mass extinction events? Why are some species more at risk of going extinct than others? Professor Erin Saupe from the Department of Earth Sciences at Oxford University is an expert on extinction. In this video, she explains how she makes use of museum collections to research extinction, and how these findings might help us prevent the loss of a vulnerable species of alligator.
Professor Erin Saupe
Visit the Ages of extinction display
Opened between 2022 and 2024, our new displays on biodiversity showcase the variety of life on Earth and consider important questions about preserving this diversity for future generations.
The Ages of extinctions display explores Earth's five major mass extinctions using specimens from the Museum's collections.
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