Small critters tend to evolve into bigger beasts, according to paleontologist Edward Cope, what is now known as Cope's Rule.
Using statistical modeling methods, a new test of this rule as it applies dinosaurs says that Cope was right -- sometimes. Which is statistically possible.
To see if Cope's rule really applies to dinosaurs, Gene Hunt and Matthew Carrano of the National Museum of Natural History (NMNH) in Washington, D.C., and Richard FitzJohn of the University of British Columbia, used dinosaur thigh bones (femurs) as proxies for animal size. They then used that femur data in their statistical model to look for two things: directional trends in size over time and whether there were any detectable upper limits for body size.
"What we did then was explore how constant a rule is this Cope's Rule trend within dinosaurs," said Hunt. They looked across the "family tree" of dinosaurs and found that some clades of dinosaurs do indeed trend larger over time, following Cope's Rule. Ceratopsids and hadrosaurs, for instance, show more increases in size than decreases over time, according to Hunt. Although birds evolved from theropod dinosaurs, the team excluded them from the study because of the evolutionary pressure birds faced to lighten up and get smaller so they could fly better.
So, nothing new. Mammals also provide plenty of classic examples of Cope's rule.
But at the upper limits to size, the results were sometimes yes, sometimes no. The four-legged sauropods (i.e., long-necked, small-headed herbivores) and ornithopod (i.e., iguanodons, ceratopsids) clades showed no indication of upper limits to how large they could evolve. And indeed, these groups contain the largest land animals that ever lived. Theropods, which include the famous Tyrannosaurus rex, on the other hand, did show what appears to be an upper limit on body size. This may not be particularly surprising, says Hunt, because theropods were bipedal, and there are physical limits to how massive you can get while still being able to move around on two legs.
As for why Cope's Rule works at all, that is not very well understood, says Hunt. "It does happen sometimes, but not always," he added. The traditional idea that somehow "bigger is better" because a bigger animal is less likely to be preyed upon is naïve, Hunt says. After all, even the biggest animals start out small enough to be preyed upon and spend a long, vulnerable, time getting gigantic.
Hunt, FitzJohn, and Carrano will be presenting the results of their study this weekend, at the annual meeting of The Geological Society of America in Charlotte.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- #GAMERGATE Style Harassment Does Not Happen in the Male Dominated Sciences
- Climate Change: It’s Only Human To Exaggerate, But Science Itself Does Not
- From Mindless Physics To Physics Of Mind
- Should First Responders Use Acupuncture And Hypnosis During Disasters?
- 24 hours with Windows 10 on a Surface Pro 3
- How Mitochondria Began - Parasitic Coevolution Gets A New Wrinkle
- Not All Fat Is Equal: Amping Up Adenosine May Melt 'Love Handles'
- "This kind of nonsense is what I am not a fan of - unfortunately, because hypnosis works so infrequently..."
- "It's because scientists don't completely cram their lectures full of politics, blacklist people..."
- "Hank I found this link on Facebook and I see on your about me page you have written a book well..."
- "No correlation? 8 of the 10 wealthiest counties voted for the president in 2008 and 2012. And they..."
- "You think this bothers me? Both gamergate and anti-gamergate supporters are behaving in immature..."
- Natural Resources Defense Council sues EPA to block rollout of Dow Enlist Duo GMO system
- Enviros file suit to block new Dow AgroSciences GMO herbicide and seeds
- Couples can protect children from devastating mutations with new IVF methods
- Food 2.0: Will farmers be able to meet the ecological challenges ahead?
- General Mills’ Cascadian Farm launches ‘bee-friendly’ campaign, GMO critics unimpressed
- Can genes pass from genetically modified food into our blood, posing dangers?
- Study shows medication is frequently, unintentionally given incorrectly to young children
- Mummy remains refute antiquity of ankylosing spondylitis
- Scientists say national Alzheimer's plan milestones must be strengthened to meet goal by 2025
- Head injury causes the immune system to attack the brain
- Viagra protects the heart beyond the bedroom