Abstract: A pygmy shrew (Suncus etruscus, ≈2 g) sustains a resting heart rate near 1,000 beats min−1 and dies within two years; an African elephant (≈4,000 kg) beats at 28 beats min−1 and lives seven decades. Their chronological lifespans differ by a factor of 35, yet each accumulates close to 109 cardiac cycles before death—a near-constancy first noted by Rubner (1908) and quantified by Lindstedt and Calder (1981) [2], but never subjected to multi-clade statistical testing, phyloge-netic correction, or explicit falsifiability criteria with a large modern dataset.