T. rex could catch a human, simulations show


By Mason Inman Video: Dinosaurs race humans, emus and ostriches Humans are fortunate not to have lived alongside Tyrannosaurus rex. The most sophisticated computer analysis of the gait of several two-legged dinosaurs suggests that even the lumbering T. rex could have kept up with an athlete. Smaller dinosaurs, like the Velociraptor, could have outpaced the fastest humans with considerable ease. Working out exactly how bipedal dinosaurs walked and ran is a vexing problem, since there are no living species with the exactly the same sort of build. The closest living relatives of such dinosaurs are emus, ostriches, and chickens, which researchers study in an effort to draw comparisons. However, previous estimates of dinosaurs’ running speeds, based on such comparisons, have tended to vary wildly. A well-regarded study published in 2002, which compared the T. rex to a chicken, suggested that this dinosaur had just enough leg muscle to lumber along at about half the running speed of a person (see T. rex caught by speed limit). William Sellers at the University of Manchester, UK, argues that this type of comparison can be misleading. “Such calculations can accurately predict the top speed of a six-tonne chicken, but dinosaurs are not built like chickens, nor do they run like them,” he says. Instead, Sellers and colleague Phillip Manning used an approach they dub “evolutionary robotics” to generate new estimates of the top speed of several two-legged dinosaurs. They built computer models featuring the leg bones, muscles, and skeletal structures of five groups of dinosaur: Tyrannosaurus, Velociraptor, Allosaurus (which looks like a miniature Tyrannosaurus), the slightly smaller Dilophosaurus, and the chicken-sized Compsognathus. To begin with, each model could move in a huge variety of different ways, too many to analysis properly. To narrow the problem down, Sellers and Manning generated a virtual population for each group, containing lots of models with slightly different gaits. They then raced these models against each other. Those that fell after only a few steps were culled while the fastest went on to spawn another generation of slightly modified gaits. After hundreds of generations, this simulated evolution arrived at an efficient, workable gait for each dinosaur. The same method has previously been used to model the gait of extinct hominids, but “we are the only people to have tried this on dinosaurs,” Sellers says. To test the approach, Sellers and Manning also created models modern humans, emus, and ostriches. Running these through the same evolutionary process, they arrived at a realistic running motion for each animal. Finally, they pitted each species against one another. The human and the Tyrannosaurus were the slowest of all, both cruising at about 18 kilometres per hour. The smaller dinosaurs ran faster, and the tiniest creature in the pack, Compsognathus, raced along at 64 kilometres per hour. “The figures we have produced are the best estimate to date as to how fast these prehistoric animals could run,” Manning says. Not everyone is convinced by the approach, however. “Their method seems to work poorly for a small, chicken-sized dinosaur,” says John Hutchinson of the Royal Veterinary College in London, UK, who led the 2002 study of T. rex. The estimate for Compsognathus is “ridiculous,” he says. Hutchinson says “evolutionary robotics” has promise and, if refined, could help predict how dinosaurs might have accelerated or jumped. “It is still a good first step,” he says. Journal reference: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2007.0846) More on these topics:
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