During the Triassic, from 250 to 200 million years ago, the ancestors of both mammals and birds became warm-blooded at the same time. Life was recovering from the Permian-Triassic mass extinction, the greatest mass extinction of all time. It killed as much as 95 percent of life, and the very few survivors were repeatedly hit by global warming and ocean acidification.
Warm bloodedness is an energy-requiring condition, but it permits the ability to compete better for resources and escape predators. Paleontologists identified warm-bloodedness and evidence for the early origin of feathers or hair in dinosaur and bird ancestors 250 million years ago. The origin of warm-bloodedness is connected to the exact time of the mass extinction.
Several special features are linked to warm-bloodedness. One is the bones inside the nose and snout, called the turbinates. These bones increase the distance that air travels into the body, allowing it to warm up on the way in. There is also the bony palate, which separates the mouth from the nose and allows for continuous breathing, even while eating. Another, which is rarely preserved in the fossil records, is the presence of fur, which acts as insulation.
At the same time, an almost instantaneous posture shift happened in both mammal and bird ancestors. Amphibians and reptiles are sprawlers, holding their limbs partly sideways. Before the crisis, most reptiles had sprawling posture; afterward, they walked upright. This may have been the first sign of a new pace of life in the Triassic. Erect postures, with the limbs immediately below their bodies, allowed birds and mammals to run faster and further. However, to fuel inner temperature control, warm-blooded animals have to eat much more than cold-blooded animals. Warm bloodedness was a dramatic evolutionary innovation, which led to emotional regulation, making it possible to take care of offspring, learn, and form consciousness.
Read more about how our mammal ancestors became warm-blooded on Phys.org.
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