However, soon after the first Jurassic Park movie was released, questions increased about how humans could survive on the same Earth as huge, fierce predators like Tyrannosaurus rex. The main catalyst for such doubts was the image of the big tyrannosaur sprinting at high speed after the fleeing jeep, bent on making a meal of its occupants.
New evidence indicates that this is just Hollywood fiction. Two specialist biomechanical researchers have shown that the famous “king tyrant lizard” would not have been able to run fast. The strength of a muscle is related to its cross-sectional area, whereas its mass is related to volume. So, as the strength needed escalates with increased weight, the mass of the muscle required increases still faster. Something like a chicken can run fast with much less than 10% of its body weight in its legs—but the more it is scaled up in size, the more that percentage rises. At the size of a T. rex, chicken-type speed would require it to have an impossible 200% of its body weight in its legs.
The new calculations suggest that the absolute maximum tyrannosaur speed was a slow (relative to its size) lumber of around 40 kph (25 mph). More realistic models of how much muscle the creature could have toted around on its legs indicate that around 15 kph (10 mph) is more likely. T. rex was simply “too big” to run, says one of the researchers. “It’s the same reason you don’t see elephants galloping or jumping over fences.”
We have already published ("The bigger they are…" 18(2):52, 1996) other reasons why T. rex would not have been a fierce chaser of people—even if it had been able to run, the slightest fall, at its size, would likely have resulted in a lethal impact. Slow, careful movements would have been mandatory. In short, large dinosaurs were much more likely to be prey for humans (e.g. hunting in groups, or using traps or poison darts) than the other way around.
- T. rex was a lumbering old slow coach, New Scientist 173(2332):6, 2 March 2002.
- T-rex was a slow, not nimble giant, Cincinnati Post, p. 10A, 28 February 2002.