Issue Date: Dec. 9, 2001

Meet the prehistoric beasts

They're not dinosaurs, but they're just as cool.

by Catherine McGrady

The names of dinosaurs roll off the tongues of even toddlers. But when it comes to the animals that roamed Earth after the dinos' extinction, most people would draw a blank. Soon, however, we'll be on a first-name basis with such bizarre creatures as the entelodont, a cross between a pig and a tank, and the gastornis, a 6-foot-tall bird.

This Sunday at 7 p.m. ET, the Discovery Channel will premiere Walking With Prehistoric Beasts, a three-hour program that uses digital technology and animatronics to illustrate the rise of mammals over the last 49 million years. Recently, we spoke with Michael Benton, head of the Earth Sciences Department at England's University of Bristol, who consulted on the project and offered this primer:

This week, the Discovery Channel revisits forgotten creatures such as the immense indricothere.

Why don't we know as much about the prehistoric beasts as we know about dinosaurs?

Maybe a hundred years ago in the States, [paleontologists] were collecting bones from both dinosaurs and large mammals in Wyoming, Montana and Colorado, and I think the public was equally excited about dinosaurs and these mammals. In the course of the last hundred years, the focus has fixed on dinosaurs, and, in the last 20 or 30 years, there's been a single-minded obsession, fueled, of course, by "Jurassic Park" and everything else.

Do you envision a "Jurassic Park"-like movie about these mammals?

There could easily be, and in many ways it would be a much more realistic film. There has been some attention in that direction -- think about the attempts to resuscitate mammoths -- because, of course, scientifically that is a much more likely thing than trying to resuscitate dinosaurs. Mammoths are as little as 10,000 years old. Chances of preservation are much better.

Besides woolly mammoths, are there other animals that most people have heard of but didn't realize were prehistoric beasts?

Saber-toothed cats like the smilodon. Maybe the woolly rhino. These are relatively recent ones -- ice age creatures. If you look back before that, people have never heard of the other creatures.

Which current animal looks most like a prehistoric beast?

I suppose something like the tapir, because it's a weird prehistoric-looking creature, probably very like some of these middle-sized mammals of the Eocene [epoch], such as the propalaeotherium. Among the prehistoric beasts we have ancestors of all the living groups, from prehistoric horses and cattle and whales and elephants to mice.

Which was the largest creature?

The largest one on land is the indricothere. It's one of the most impressive -- some overgrown elephant crossed with a giraffe but vastly larger than an elephant. Hugely high. It could peer over a two-story house. The indricothere is dinosaur-like in dimension but gives you a double take because, unlike a dinosaur, which is remote and distant, the indricothere looks familiar because, of course, it is a rhinoceros. It's the type of thing you can see at the zoo, yet twice the size.

Which was the smallest?

Some little shrew-like things; you could fit 10 on your hand. Obviously, people are familiar with mice. Well, there are tiny shrews that are a tenth of that size. They just weigh a few grams. The mammals have this astonishing range of size, but there's never been a dinosaur anything like that. The smallest dinosaur was the size of a turkey.

How and when did the prehistoric beasts show up on Earth?

The mammals were around at the time of the dinosaurs. Then the dinosaurs died out for whatever reason, and the mammals that were already there survived -- probably at least because they were small and warmblooded. It's very interesting for us to imagine what the world was like immediately after the dinosaurs went: an empty, echoing, dark, cold place. These little mammals, the largest of which was the size of a cat, found the world empty, and since competition was removed they could do all kinds of things they had been prevented from doing. You had a phase of very rapid evolution, so that in about 5 or 10 million years you have gone from shrew, rat and cat to bat, whale and tree-climbing primate.

Which ones survived the longest?

The longest surviving mammal group would be the small insectivore, the shrew-like creature. And of course, to our eyes, they haven't changed much, and because what they do is very successful -- they hunt insects, particularly at night -- they've carried on. It's hard to identify any particular species that has survived for a long time because most mammal species only last for 2 or 3 million years at the most, and then they are replaced.

Did these beasts live as long as the dinosaurs?

Some lived with the dinosaurs and continued into the post-dinosaur world. The dinosaurs arrived about 230 million years ago, and the big extinction event was 65 million years ago. Interestingly, the first mammals arrived at the same time, so they were there with the dinosaurs, but the mammals were held in check. Dinosaurs were so good at being dinosaurs that the mammals were prevented from doing much until the dinosaurs disappeared. [Australopithecus, the earliest human-like creature, first appeared 4 million years ago.]

What does this teach us about survival?

If you look at the story of the mammals in the last 65 million years, they show us a pattern of what happens after an extinction. You can have very rapid evolution of whatever group happens to survive, and that phase is what we see in the first 5 to 10 million years, as is shown on our show. You can get all kinds of weird creatures popping up in that time. Then there's a sorting-out phase where a lot of those early-to-originate groups disappear and the successful designs, like monkeys and horses and whales and bats, survive.

Which prehistoric beast would make an appealing stuffed animal?

If it's got to be round and fluffy, I don't know. Some of the hero ones would not be very attractive -- like the andrewsarchus, the carnivorous pig-like creature. I think boys might like that, but it wouldn't make a good bed companion. It might scare you.