Beats

a whole life of heartbeats. how high will the jar fill?

shadow-puppet animals from a shrew to an elephant to a person; guess how high a whole life of heartbeats fills the jar

Small mammals have fast hearts and short lives; big ones have slow hearts and long lives, and the two roughly cancel, so a mammal's life holds on the order of a billion heartbeats. Each total here is a resting heart rate times the longest life on record for the species (house mouse, African elephant, Etruscan shrew, cat, horse, giraffe, chimpanzee, person; both numbers from Taye 2026, compiled from AnAge and PanTHERIA), so it is a rough sketch, not any one animal's count: a real heart speeds up and slows down, and most lives are shorter than the record. Across 46 non-primate mammals the totals average about a billion and 93% fall within a factor of two of that; Levine (1997) found 0.73 billion, give or take 0.56. Primates live far longer than their hearts predict, and people most of all: 70 a minute for 122 years is 4.5 billion.

Concepts: biology, scaling.

An interactive you play with one thumb, on Wundr.