T. Rex Quicker Than Fastest Humans, Study Says

John Roach
for National Geographic News
August 23, 2007
Today's top athletes would be no contest for meat-eating dinosaurs that ran on two feet, according to new computer simulations of how the extinct predators moved.

Even a six-ton Tyrannosaurus rex, long considered a lumbering beast, could reach a top speed of 18 miles an hour (29 kilometers an hour), according to the simulations.

Fit athletes run just a fraction slower.

"Now I'm no slouch, I can run, but … I think I'd end up being lunch for T. rex," said Phillip Manning, a paleontologist at Britain's University of Manchester.

Manning and co-author William Sellers describe the simulations in a paper published Wednesday in the journal Proceedings of the Royal Society B.

Supercomputer Simulations

The simulations were created on a supercomputer model that crunches information on skeletal and muscular structure.

The program requires about a week to simulate the animals' method of movement, or gait.

"There are an awful lot of ways that you can activate muscles in a gait cycle, and the vast majority of them lead to an animal falling over very quickly," Sellers said.

The computer model takes the best gait cycle from each batch of about a thousand attempts as the starting point for each new batch, eventually finding the most likely simulation.

"It's a very good way of searching through effectively infinite space to find good solutions," Sellers said.

"Obviously, we can't guarantee these are the best solutions."

The researchers first tested the model by applying it to living animals, including humans, ostriches, and the Australian emu.

"We got the information from modern animals, which we then put into the model in the same way we would for an extinct animal, and the speeds were pretty accurate," Manning said. "They were in tune with what we'd expect for the modern species."

An ostrich, the fastest two-footed runner alive today, topped out at 34 miles an hour (55 kilometers an hour) in the model. A fit human came in a smidge slower than T. rex.

The team then plugged in the details of five meat-eating dinosaurs.

The skeletal information came from the fossil record, while muscle data was inferred from what's known about dinosaurs' living relatives, especially birds and crocodiles, Sellers explained.

According to the simulations, the chicken-size Compsognathus ranked as the fastest dinosaur, reaching a top speed of nearly 40 miles an hour (64 kilometers an hour).

Manning said the top speeds are likely conservative, since the strongest possible muscle and bone configurations have yet to be modeled.

The team is currently working with the National Geographic Society to create a 3-D model of how dinosaurs moved. It involves more muscles and thus even more complicated calculations, Sellers noted.


"The idea there is to produce something that is actually more accurate kinematically, [that] actually produces more realistic movements," Sellers said.

Overconfident Results?

John Hutchinson is an expert in the biomechanics of living and extinct animals at the University of London's Royal Veterinary College. He complimented the recent simulation as an advance in understanding dino locomotion.

"My previous work just looked at one part of the step," he said.

But, he said, the method requires many assumptions about the skeletal and muscular structure of these extinct animals, assumptions that need to be carefully considered before firm conclusions are drawn.

"I've never even done or trusted approaches like this, because there're a lot of assumptions that go into these models and it's very easy to get misled or get overconfident about the results," he noted.

Nevertheless, Hutchinson said, most of the speeds obtained from the computer model are in line with the range of speeds suggested from his own modeling studies, although he disagrees with the use of a definitive top speed.

"There's no way you can be that precise for an extinct animal," he said.

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