Were Dinosaurs Cold-Blooded?
A paper in Science1 shows that at least one dinosaur species came in large and small forms. Martin Sander and Nicole Klein studied fibrolammelar bone on plateosaurs (a heavy two-legged dinosaur with an elephant-like body and long neck), and found that the growth rates were poorly correlated with body size. Some plateosaurs were full-grown at five meters, others at twice as big. It suggests that the creatures were dependent on environmental factors for warmth. This calls into question the conventional wisdom, held for 20 years, that dinosaurs were warm-blooded, because most warm-blooded creatures grow steadily to their adult size (see the BBC News and National Geographic News).
This find also suggests that the earliest dinosaurs were not the two-legged fast-running kind, but the four-legged, lumbering kind. Sander calls this a paradigm shift: “The idea that it [the earliest dinosaur] walked on two legs has been pretty much dogma for the last 20 years.”
The paper also calls into question some assumptions about dinosaur evolution. “Since the common reptilian ancestor of the dinosaurs, and their closest relatives, the pterosaurs, or flying reptiles, was believed to have been warm-blooded,” the BBC News article states, “the [University of] Bonn discovery could throw ideas about their evolution into disarray.” To salvage the idea of warm-blooded dinosaurs, some are seriously suggesting warm-bloodedness evolved multiple times: “My hunch right now is that maybe there was repeated evolution of warm-bloodedness,” Martin Sander told BBC News. If so, warm-bloodedness was not inherited from a common ancestor.
Carolyn Gramling, commenting on this paper in the same issue of Science,2 quoted Thomas Holtz (U of Maryland) remarking about how little we still know about early dinosaur evolution. “There has been the tendency to infer that features found in all advanced dinosaurs were found in all of their ancestors,” he said. “This emphasizes the importance of tree-based thinking. We have to look at as many branches of the evolutionary tree to get as big a picture as possible.”
1P. Martin Sander and Nicole Klein, “Developmental Plasticity in the Life History of a Prosauropod Dinosaur,” Science 16 December 2005: Vol. 310. no. 5755, pp. 1800 – 1802, DOI: 10.1126/science.1120125.
For more on tree-thinking, see the 11/14/2005 story. Tree thinking is an escape into the briar patch (11/26/2005) where Darwinists can hide from scrutiny within the tangled web of varying interpretations.
Warm-bloodedness is not just a trait; it is a complex suite of traits involving fine-tuning of the circulatory system, the developmental system, the respiratory system, the nervous system, the skin – basically, of the whole animal. When evolutionists want to take such an improbable event (in evolutionary terms) and multiply it several times just to keep their common-ancestry belief intact, it becomes evidence once again that evolution is a theory in crisis.