ABSOLUTELY EVERYTHING

Each month we feature an amazing story from world history taken from the bestselling book by Christopher Lloyd, with illustrations by Andy Forshaw. This month: a mysterious disappearance of giant animals

Over the last 2.6 million years of Earth’s history, glaciers have come and gone, sometimes covering the northern parts of the world with ice for thousands of years at a time. Each time the climate has changed, individual species, including humans, adapted to different climates, hot or cold. And when one species died out, others evolved to take its place.

When the Earth was warming up from a frozen time called the last glacial maximum, the story should have been just the same. But it wasn’t. Dozens of large mammals were alive and well all over the world when the warming started. Some of them had existed for tens of millions of years. Yet, between about 13,000 years ago and about 8,000 years ago, most of the biggest of them died out. This disaster is known as the Pleistocene Extinction after the era when it happened.

In North and South America, horses, big cats, elephants, mammoths and mastodons, camels, great bears, giant beavers, peccaries (pig-like mammals), giant ground sloths and the glyptodont – an armadillo the size of a pick-up truck which is shown on the opposite page – all mysteriously disappeared. In all, about three-quarters of the large mammals became extinct. When the Pleistocene Extinction was over, very few animals in the Americas were bigger than a turkey. Even the beavers and bears that made it through the crisis were smaller cousins of those giants that once existed. An illustration of animals alive on Earth before the Pleistocene Extinction.

PERCENTAGE OF LARGE MAMMALS THAT WENT EXTINCT AFTER THE PLEISTOCENE EXTINCTION

1OO

8O

6O

4O

2O

Pretty much the same thing happened in Australia, although the extinctions there started earlier. Victims included the giant kangaroo, a rhino-sized wombat and its relatives, and a fierce marsupial lion. Huge reptiles died off, too, including the giant horned tortoise and some gigantic crocodiles.

Large animals went extinct in other parts of the world as well. The southern half of Africa lost fewer than the rest. But even there about one in every six big mammal species went extinct. Experts find this whole worldwide extinction event puzzling because no new large animals arose to take the places of those that had disappeared.

What on Earth was going on? Some experts point to global warming, which changed environments worldwide, even where it had never been cold. As a result, large animals lost their habitats. But climate alone doesn’t explain the timing of some of the extinctions.

In many places, the extinctions followed the arrival of humans in the area. Maybe they were to blame. Could humans have hunted all these giants to extinction?

You can tell the age of a woolly mammoth from the rings of its tusks, like the rings of a tree!

Or did fire-lighting humans burn so many animal habitats so quickly that the animals couldn’t survive?

This hypothesis might explain why elephants, rhinos and big cats survived in Africa when animals like them went extinct elsewhere. African animals and humans had evolved together over millions of years. Could they have found a balance that let both survive?

The point of having a hypothesis or theory is to test it against other evidence, to ask questions that might prove or disprove it. For example, if

Imagine bumping into a 3-metre-wide glyptodont! It had the heaviest armour plate protection of any Ice Age creature. By 1O,OOO years ago these giants had gone extinct like many other large animals around the world.

humans caused the extinction, why did Africa lose any animals at all? As often happens in science, we don’t know all the answers. We just have to keep making hypotheses and questioning them. There could be more than one cause. Perhaps humans and climate change are both to blame for the Pleistocene Extinction.

The part we humans played may have been our first big impact on the Earth’s environment. It was certainly not the last. :

Focus the camera of a smartphone or tablet on this QR code to listen to an audio recording of the author reading this book extract.