Big and beastly

IN an Eocene forest nearly 50 million years ago, a leptictidium sits frozen with fear. You can almost see the small, rodent-like animal's long, insect-feeding snout twitching with fright. On either side of it, poised ready to spring, are two giant gastornis - fearsome, predatory flightless birds nearly the height of a man, their wicked beaks gaping wide as they prepare for the kill.

If you thought the age of the dinosaurs held the monopoly on weird, wonderful and wicked beasts, think again. In the 65 million years that have passed since they died out, new beasts have evolved and taken their place - then evolved again and again as the world around them changed, right down to the present day.

Many of the creatures who succeeded the dinosaurs were just as gigantic, fierce or bizarre as their better-known predecessors. They inhabited a world that was dominated by a different kind of animal - the mammal. And out of their number evolved the fiercest, most ruthless killer ever to stalk the face of the planet: man.

Now, a new exhibition in York brings the world of these forgotten fabulous beasts back to life. The York Museums Trust's Walking With Beasts exhibition in St Mary's Church, Castlegate, has been put on in association with the BBC, which produced the TV series. It features life-size models of the creatures used in the making of the series, video footage and giant wall posters recreating scenes of ancient life.

Then there are real fossils, a wealth of information panels, and hands-on interactive displays that allow you to do everything from watching how fossils were made to recreating your own terror bird or elephant ancestor.

There's also a section devoted to the making of the TV series, showing how the bizarre beasts recreated so memorably on screen were brought to life using the latest computer animation techniques and a mixture of "science, observation and guesswork".

The exhibition, says my guide Barry Cross, aims to "fill in the gaps" between the dinosaurs and the world of familiar beasts we live in today. "It gives us an idea of where all the beasts we see around us today came from - including our own ancestors," he says.

A video loop taken from the BBC series sets the scene. When a giant asteroid struck the earth 65 million years ago and finally put paid to the age of dinosaurs, says Kenneth Branagh's voice, almost every animal that weighed more than 10kg was wiped out. It left, he says, a "world of little beasts: among them mammals".

Fast forward 16 million years to the Eocene epoch. It is 49 million years ago, and a bewildering variety of new life has evolved. The world is warm, and covered in forests. Mammals are everywhere: but they are still mainly small - rodents, bats and primates ideally suited to life among and below the trees.

There are some big killers, however - giant flightless birds, the gastornis. A whole wall is devoted to a huge tableaux of the two killers birds about to pounce on the hapless leptictidium. Video footage shows them in action. Panels provide information - the most startling of which is that the closest living relative of these man-sized birds with their mighty, three-clawed hind legs is the harmless moorhen. It makes you think.

Moving on in time to the Upper Eocene, ten million years or so later, the fearsome shape of an andrewsarchus looms up. It's a big new mammal: a wolf-like creature of massive proportions with a bone-crunching jaw a metre long. The largest carnivorous land mammal that ever lived, it owes its name to the palaentologist Ray Chapman Andrews - the role model, apparently, for Indiana Jones. More intriguingly, despite its wolf-like appearance its closest living relative is somehow the whale. The mind boggles.

Next, it's the Miocene, a mere 24 million years ago. The climate is cooler and more settled. The polar ice caps have expanded, the sea-level has fallen, and a new plant has made its appearance: grass. Much of the planet, however, is covered in broad-leaved woodland.

Among the creatures that walk the face of this new, cooler earth is the entelodont, a monstrous forerunner of the pig with massive shoulders and what must be the ugliest mug ever to have graced a living creature. It lived on roots and tubers, and by scavenging corpses - but it was still a ferocious beast. Scars found on the animals' fossilised skulls revealed they fought savagely among themselves, a panel says.

By the Pliocene, just a few million years ago, animals more familiar to us today are making an appearance. Great cats, giant elephant ancestors - and an upright ape, australopithecus, which has come down from the trees to walk the African plains. "The Prey's Revenge", says a wall panel, showing a picture of a leopard-like cat munching on one of these primitive apes. Revenge, because in just a very few million years, they would have evolved into the most dominant species on the planet: man.

As the exhibition nears the present day, just a few tens or hundreds of thousands of year ago, spectacular beasts still continue to stalk the earth: phorusrhacos, the terror bird, another vicious flightless bird 2.5 metres tall at the shoulder and equipped with a cruel, hooked beak and a headcrest of feathers; smilodon, the sabre-tooth, a fossil skeleton of which stands with its six-inch-long yellow teeth gleaming; and the woolly mammoth, a red, hairy beast the size and shape of an elephant which our ancestors hunted in the days of the ice age.

Walking With Beasts is a humbling journey through 50 million years of evolution that leaves you wondering how, in the face of competition from such fearsome creatures, our ancestors ever managed to survive long enough to become the masters of the world we are today.

It says much about the kind of creatures we are that we did.

- Walking With Beasts runs in St Mary's Church, Castlegate, York until November 2. It is open daily from 10am to 5pm. Admission: adults £3.50; concessions £2.50; family tickets (two adults and two concessions) £10.

Updated: 09:09 Saturday, July 05, 2003