Endothermy, colloquially known as warm-bloodedness, was a major breakthrough in the history of life on Earth. It gave rise to the active lifestyle of birds and mammals. But how did it evolve? Research into this question has been ongoing for decades, though in the eyes of evolutionary physiologist Barry Gordon Lovegrove, the field has stagnated amidst competing single-cause hypotheses that all try to find that one killer explanation. In his wide-ranging Fires of Life, he brings together many disparate strands of research and gives an overview of our thinking on the evolution of endothermy in mammals and birds. Providing food for thought for students in this field, it also is a great overview for the general reader that stands out for its superbly accessible writing.