Friday 26 June, 2009

UK
Science/Nature

Artist’s conception of a Diplodocus dinosaur.

By Andrew Halloway

New research suggests that scientists have got their sums wrong – the biggest dinosaurs weren’t half as big as they’ve been telling us for all these years.

It gives a whole new meaning to ‘telling a whopper’, but a new study suggests that giant creatures like the long-necked, long-tailed Diplodicus probably weighed only half what was previously thought.

So, bin all those artists’ impressions and BBC special effects of dinosaurs looking like hippos on steroids and behold the new dinosaur-lite: skinny and spindly.

Mind you, these behemoths were still as long as their skeletons suggest, but they’d obviously been to the gym rather than stuffing down the cream cakes.

A new equation for calculating dinosaur mass based on the skeletons shows that scientists have overestimated the weight of many dinosaurs.

Geoffrey Birchard, a biologist at George Mason University in Virginia, and co-author of a paper published this month in the Journal of Zoology, tries to put a brave face on the previous miscalculations: “They might be half as big, but half of something that’s really huge is still really huge.”

For example, one of the largest of the dinosaurs, Apatosaurus louisae, is often estimated at 42 tons (38,000 kg). But the new equation rectifies that to about 20 tons (18,000 kg) – less than half. Some other examples include:

• Giraffatitan brancai (Brachiosaurus) – old: 35 tons (32,000 kg); new: 18 tons (16,000 kg)
  
• Lourinhasaurus alenquerensis – old: 32 tons (29,000 kg); new: 17 tons (15,000 kg)
  
• Styracosaurus albertensis – old: 4.6 tons (4,200 kg); new: 3.6 tons (3,300 kg)
  
• Diplodocus sp. – old: 6.1 tons (5,500 kg); new: 4.4 tons (4,000 kg)
  

Birchard and collaborators Gary Packard and Thomas Boardman of Colorado State University spotted the mistake in the original equation when they used it to calculate the weight of today’s animals, such as elephants, from their skeletons. They found that it severely overestimated their mass. How come no-one thought of doing that as a test… long ago?

So Birchard et al revised the statistical model for predicting the mass of an animal, based on the width of its bones, and lo and behold the dinosaurs no longer have to attend Weightwatchers.

But we are not just talking about the fat content of these dinosaur bodies. The massive mistake in estimates means that the whole biology of dinosaurs may need reassessing.

“Think about an animal that big – they would have had to have certain amounts of muscle to move their mass,” Birchard says. “If their mass is lower, the amount of muscle they would have had to have is significantly less. The amount of oxygen they would need could be interpreted to be much less because there’s much less tissue to supply with oxygen.” And then there’s the issue of whether the bones themselves really weighed as much as previously thought. And so on.

In other words, scientists are admitting they don’t really know as much as they thought they did.

Now, I admire the great success of science in general, but I think this large blooper by scientists allows us a bit of window into the reality behind the science news headlines.

Scientists often pontificate about the ‘facts’ and use phrases like ‘we know this happened’ when really they are talking about their best guess. Too often, a few years down the line, what was once foisted on the public as a certainty is overturned and discredited. It is the way science works. So we should take some statements about ‘facts’ with a pinch of salt.

This is especially true when it comes to historical science. There is a big difference between historical science and empirical science. Empirical science is about things that can be observed, tested and re-tested in the lab today, and is responsible for the great technological advances that characterise our modern world.

Historical science, however, which theorises about the past, should be held more tentatively, as it is being continually revised and relies much more on best guesses and assumptions. Much as we’d like to, you can’t travel back to the past to observe what really happened.

So where am I going with this? Well, Darwinian evolution is the biggest historical science going, relying on more guesswork and wishful thinking than any other area of science. Yet atheist scientists are always saying it is a foregone conclusion and anyone who thinks otherwise must be stupid.

Well, if scientists are capable of getting the size of dinosaurs so wrong, what other theories about fossils and pre-history are they capable of getting wrong?

Perhaps next time you hear Richard Dawkins wittering on about the so-called ‘facts’ of evolution, you might be tempted to remember this dinosaur downsizing debacle, and conclude that he may only ‘know for sure’ half of what he claims to.

Photo: Julius T. Csotonyi