Where Do We Go From Here?SUMMARY OF THE DEBATE
The problem is far from solved, as you may guess from what you've seen so far. Many questions about endothermy and ectothermy in modern animals remain to be solved, such as:
"How did endothermy evolve in mammals?"
Yes, it's a confusing and frustrating controversy, and the two (among the many) diametrically opposed sides of the argument help to make it even more complex. Are some of them missing something that paleontologists outside of the debate see? Maybe. There is strong evidence from both sides that dinosaurs in general had a different physiology from either mammals or "typical reptiles." Endothermy did evolve from ectothermy, and birds (endotherms) did evolve from dinosaurs, which we know came from ectothermic ancestors sometime in the distant past. Dinosaurs were quite diverse in size and form; their physiologies must have differed as well, just like whales, bats, and horses have different physiologies. We have found examples of physiologies outside of the artificial "endotherm-ectotherm" dichotomy: elevated metabolic rates and even homeothermy exist in some species of sea turtles, sharks, pythons, tuna, and even insects. Some mammals, such as the monotremes have lower metabolic rates, and seem closer to an ectothermic condition. As long as we do not understand endothermy and how it evolves, we have little chance of understanding what animals were endotherms or not. And, above all, there is no reason why dinosaurs could not have had some sort of intermediate physiology between endothermy and ectothermy. In fact, it seems more likely than anything that they did have some unknown sort of physiological system that worked well (they did dominate the realm of the terrestrial vertebrates for some 170 million years!). Some dinosaurs could have been normal ectotherms, and some could have been endotherms. Yes, it's a messy issue.
We'll close by listing the five main sides that paleontologists have taken since the issue began. Feel free to make up your own mind who may be right!
Top five current hypotheses
Back to DinoBuzz
Learn more about the Dinosauria