So scientists took a different tack. They pumped ordinary chicks full of growth hormones until they each weighed an elephantine six tonnes. They had massive drumsticks, enough for generations of chicken pies - and they were too gross to run away. Such fantasies plague the minds of scientists trying to bring dinosaurs back to life: how did large dinosaurs move and behave.
For, when stripped down to its bony basics, Tyrannosaurus rex was not very different from a six-tonne chicken. John R Hutchinson and Mariano Garcia of Stanford University use this comparison to work out whether
T. rex could have been a fast runner, and they present their findings in today's Nature. The answer is, probably, "no". In fact, it is amazing that T. rex could even walk. All scientists agree that small, bipedal, carnivorous dinosaurs - such as Velociraptor - would have been capable runners.
Matters are less clear for very large dinosaurs such as T. rex, some of which could have weighed as much as the modified chickens. Some scientists think the giant T. rex could only have been a plodder, reduced to scavenging carcasses left behind by more agile hunters. Others look at rex's nimble, birdlike feet and graceful carriage (for none succeeded so well in the deportment department) and have it that T. rex could have hopped gaily along like the proverbial spring chicken. This is the image from Jurassic Park, in which an angry rex chases a speeding jeep, intent on taking a big chunk out of Jeff Goldblum.
But as animals increase in size, the amount of muscle they need to move increases disproportionately. Big animals need more muscle to move than small ones. But need this be a restriction? Hutchinson and Garcia show that there is more to size than... well, size.
The argument is all about muscle - specifically, how much of its leg muscles can an animal afford to devote to putting one leg in front of the other. Normal-sized chickens and other running birds devote just a few per cent of their body mass to such muscles. But scale a chicken to the size of a Tyrannosaurus, and it would have to devote almost twice its body mass to limb muscle to run.
A gigantic catering chicken would not even have been able to stand on its own two feet. In real life, however, T. rex thrived, toddling around the Cretaceous landscape with conspicuous success. It did not sit there, musclebound, waiting for food to come its way. Yet to have seen T. rex running at speed would be to see an elephant fly. Why? The best reconstructions, based on anatomy, suggest that T. rex would have put between 10% and 20% of its body mass into leg muscle.
Yet Hutchinson and Garcia's sophisticated model suggests that for it to have been a speedy gonzalez, the figure would have been close to 80%, which sounds too musclebound to be credible. In short, there is no way T. rex could have run very fast, or at all. But given that a 6,000kg chicken could hardly have moved, it is remarkable that T. rex was as mobile as it was.
The reason is, undoubtedly, alterations in proportion: mainly a posture in which its limbs were held straight rather than flexed, more like an elephant than a chicken. So Jeff Goldblum was safe. He could have called the marauding dinosaur any rude name he chose ("chicken" would have been a good start), because, like all overweight bullies, Tyrannosaurus rex couldn't have run for toffee. He was just a six-tonne turkey.
· Henry Gee is a senior editor of Nature