From The Dinosaur Papers edited by Weishampel and White
Louis Antoine Marie Joseph Dollo completed his degree in civil engineering in 1877. He devoted five years to industrial pursuits, then left his homeland of France for Belgium. Working at the Musée Royal d'Histoire Naturelle de Belgique, he concentrated primarily on Iguanodon, the dinosaur originally discovered and named by Gideon Mantell.
From The Dinosaur Papers edited by Weishampel and White |
Dollo's timing was fortunate. In 1878, an underground coal mine in southeast Belgium proved to be the final resting place of 31 well-preserved Iguanodon dinosaurs. Dollo oversaw the preparation and articulation of the skeletons, and in 1882, published the first of several papers about the fossils. He discussed the preservation of the skeletons, identified two separate species and addressed their posture. Dollo advocated a bipedal, kangaroo-like stance for Iguanodon. The posture has since been overturned, but paleontologists do acknowledge that Iguanodon probably stood primarily on its hind legs. Dollo speculated that Iguanodon was amphibious and used its powerful tail to swim like crocodiles. He also found that the "horn" that Mantell originally placed on the animal's snout was really a thumb spike.
It's easy to shrug off Dollo's task of mounting skeletons as no big deal, but articulating dinosaur bones is no trivial task. Fossil bones have two annoying characteristics that are individually irritating, and together produce a synergy of aggravation: They are very heavy and they are very fragile. Dollo put together a system of ropes, pulleys and beams to hoist the beefy bones into position before hammering them into place. The system was labor-intensive, but it worked. Today, paleontologists often use light, replaceable casts.
Dollo's engineering expertise was as evident in his writing as it was in his fossil mounts. His writing was concise, direct and usually in numbered paragraphs or lists. When addressing two different forms of Iguanodon, he reasoned as follows.
Besides his extensive studies of Iguanodon, Dollo helped establish what is now known as paleobiology. He found that detailed studies of fossil anatomy could be used to reconstruct the adaptations of extinct animals. In 1893, he established Dollo's Law, also known as the Law of Irreversible Evolution. He hypothesized that organisms could evolve particular specializations but could not later lose those specializations. Horses, for example, could not re-evolve the side toes they had already lost.
More than a century later, biologists debated whether Dollo's Law was true. A paper published in 2009 indicated that, on a molecular level, it probably is. Glucocorticoid receptors are proteins that help most vertebrates cope with stressful or dangerous situations by snaring cortisol. Researchers reconstructed the protein's gene history, including the mutations it had likely undergone then reversed some of the mutations. Without key mutations that enabled the protein to specialize in cortisol grabbing, the protein was useless for any purpose. Other mutations that may have refined the process added extra features to the protein that got in the way of anything else. Although these other mutations could theoretically be reversed, they weren't likely to be favored by natural selection.
For more information:
The Dinosaur Papers edited by Weishampel and White
The Reign of the Dinosaurs by Jean-Guy Michard
"The Colossal Stranger: Andrew Carnegie and Diplodocus Intrude European Culture, 1904-1912" by Ilja Nieuwland in Endeavour June 2010
Can Evolution Run in Reverse? A Study Says It's a One-Way Street (http://www.nytimes.com/2009/09/29/science/29evol.html)
Narrative text and graphic design © by Michon Scott - Updated July 12, 2010