The evolution of endothermy (thermoregulation by metabolic means) represents a major transition in vertebrate history. However, the process of endothermy evolution and its timeline in birds and mammals remains controversial. In a new report on Science Advances, Enrico L. Rezende and a team of researchers at the Center of Applied Ecology and Sustainability, and the Institute of Environmental and Evolutionary Sciences in Chile, combined a heat transfer model with theropod body size data. The researchers then reconstructed the evolution of metabolic rates along the bird stem lineage. The results suggested that a reduction in size constituted the path of least resistance for endothermy to evolve—maximizing thermal niche expansion, while reducing costs of elevated energy requirements.
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Source: Phys.org