Galloping Giants

Was T. rex a speedster after all?



In the blockbuster movie Jurassic Park, a huge Tyrannosaurus rex was shown not only gobbling up humans, but chasing after them in a speeding jeep at perhaps 70 km/h (45 mph). Such fearsome predatory capacity raised the question in many minds as to how humans would have survived in a world that once included such seemingly swift and mighty carnivores. However, not long after that, we featured in our magazine Creation (and later, on our website) the results of scientific analysis (by evolution-believers) that debunked this image.1

Dinosaur expert James Farlow, of Indiana-Purdue University in the USA, and a colleague, concluded that the sheer size and weight of a large T. rex meant that it could never have achieved such speeds. As an animal’s size varies, everything else does not scale up or down in proportion. Thus, if a horse fell down a mineshaft deep enough for it to break limb bones, the same fall by a mouse would leave it unharmed. An elephant, on the other hand, would likely splatter and die instantly from the same misadventure.

For the same reason, while elephants can reach appreciable speeds at full gallop, they can’t hurdle over fences that a horse would take in its stride. And their speeds relative to their body size are pathetic compared to many of the most humble insects.

Besides stating that strength of a tyrannosaur’s thighbone was not sufficient to support fast running, Farlow’s chief conclusion was that the limiting factor on T. rex’s speed was not simply one of relative bulk, but a real danger of death in the event of a fall. As we reported in our magazine article on the subject:

‘… simply tripping [a charging T. rex] up or getting its feet somehow tangled would have been enough to smash it into a lifeless heap.
‘Farlow and a physicist colleague have calculated that the huge beast was so heavy and high that if it tripped and fell while running, a tumbling tyrannosaur’ torso would have slammed into the ground at a deceleration of 6g (six times the acceleration due to gravity). Its tiny front legs would have been inadequate to substantially break its fall.
‘This means that in dry soil, its body would have made an impact crater 20 centimetres (eight inches) deep! Its head would have hit with a brain-shattering impact of more than twice as much force.’

The relevance of all this to creation/evolution is, of course, that humans would have little to fear from this dinosaur that could be killed by merely tripping it up, and which would likely have moved very slowly to avoid any risk of an accidental stumble.

This was reinforced a bit later by a report on the discovery of fossil allosaurs (a smaller version of tyrannosaurs) which showed evidence of ribcage fractures from just such falling-type injuries. Their smaller size meant that the injuries were not severe enough to kill them.2

We also reported in 2001 on the comment by ‘Dinosaur Jack’ Horner, the famous fossil expert after whom the hero in Jurassic Park was modeled, that T. rex ‘couldn’t run’, because its thighbone was longer than its shinbone, contrary to the pattern in fast bipedal predators of today.

In late August 2007, however, research results were published in the Proceedings of the Royal Society B, which were supposed to show that T. rex was a lot faster than thought.3

This was claimed to be the most accurate assessment of dinosaur speeds to date; it suggests that T. rex could reach speeds of nearly 30 km/h (18 mph). While not exactly in speeding-jeep territory, this is slightly faster than a fit sportsman can run. It’s reasonable to ask whether this should cause one to discard the previous ‘ultra-low-speed’ assessments. Maybe—but first it’s worth briefly discussing this 2007 research, which was based on computer models of the biomechanics. While this approach accurately predicted human top speeds, and included many more variables at a higher degree of sophistication than previous such attempts, there is no indication that the above issues, particularly the crucial one of tripping and falling to death, were taken into account.

So even if tyrannosaurs were biomechanically capable of these sorts of speeds (by no means a settled question) natural selection (a fact of life) would actually tend to eliminate tyrannosaurs which were programmed to habitually charge after their prey at top speeds. And their short arms would have been nearly useless in breaking their fall.

Incidentally, many have suggested that T. rex was most likely a scavenger, anyway, not a hunter, given for example the apparently poor eyesight suggested by fossil remains.4

Finally, even in the unlikely event that tyrannosaurs were capable of outrunning and killing humans, it would not mean that humans would be wiped out by these beasts, and thus be an argument against the biblical coexistence of humans and dinosaurs. Elephants can outrun and even kill humans. Yet human ingenuity, even when only spears, rocks and traps were available, has always seen elephants at greater risk from humans than vice versa. There is no reason to think that the same would not have been true of even the largest carnivorous dinosaurs.

Published: 7 September 2007


  1. See C.Wieland, The bigger they are … March, 1996 Return to text.
  2. ‘X-rays of one fossilized specimen showed 14 ribs with healed fractures. These fractures were most likely caused by bellyflops that happened while running
    Return to text.
  3. www.physorg.com/news106988114.html, August 22, 2007 Return to text.
  4. T. rex toothmarks have been found in Triceratops bones, but none to date with the crucial ‘kill’ pattern. Return to text.