Biological Sciences, British Antarctic Survey, NERC, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
Biol Rev Camb Philos Soc. 2010 Nov;85(4):703-27. doi: 10.1111/j.1469-185X.2010.00122.x.
Endothermy has evolved at least twice, in the precursors to modern mammals and birds. The most widely accepted explanation for the evolution of endothermy has been selection for enhanced aerobic capacity. We review this hypothesis in the light of advances in our understanding of ATP generation by mitochondria and muscle performance. Together with the development of isotope-based techniques for the measurement of metabolic rate in free-ranging vertebrates these have confirmed the importance of aerobic scope in the evolution of endothermy: absolute aerobic scope, ATP generation by mitochondria and muscle power output are all strongly temperature-dependent, indicating that there would have been significant improvement in whole-organism locomotor ability with a warmer body. New data on mitochondrial ATP generation and proton leak suggest that the thermal physiology of mitochondria may differ between organisms of contrasting ecology and thermal flexibility. Together with recent biophysical modelling, this strengthens the long-held view that endothermy originated in smaller, active eurythermal ectotherms living in a cool but variable thermal environment. We propose that rather than being a secondary consequence of the evolution of an enhanced aerobic scope, a warmer body was the means by which that enhanced aerobic scope was achieved. This modified hypothesis requires that the rise in metabolic rate and the insulation necessary to retain metabolic heat arose early in the lineages leading to birds and mammals. Large dinosaurs were warm, but were not endotherms, and the metabolic status of pterosaurs remains unresolved.
温血动物的进化至少发生过两次，一次发生在现代哺乳动物和鸟类的祖先中。对于温血动物进化的最广泛接受的解释是选择增强有氧能力。我们根据对线粒体和肌肉性能产生 ATP 的理解的进展来回顾这一假设。随着用于测量自由生活脊椎动物代谢率的同位素技术的发展，这些技术证实了有氧范围在温血动物进化中的重要性：绝对有氧范围、线粒体产生的 ATP 和肌肉功率输出都强烈依赖于温度，这表明随着体温升高，整个生物体的运动能力将得到显著提高。关于线粒体 ATP 产生和质子泄漏的新数据表明，不同生态和热灵活性的生物中线粒体的热生理学可能不同。结合最近的生物物理建模，这加强了长期以来的观点，即温血动物起源于生活在凉爽但变化的热环境中的较小、活跃的广温性冷血动物。我们提出，体温升高并不是增强有氧能力进化的次要结果，而是实现这种增强有氧能力的手段。这个经过修改的假设要求，在导致鸟类和哺乳动物的进化过程中，代谢率的升高和保留代谢热所需的绝缘性必须很早就出现。大型恐龙是温暖的，但它们不是温血动物，翼龙的代谢状态仍未解决。
