Introduction
What are the "Billion Heart Beats"? The term refers to an observation/rule that all mammals will have an expected life-span that will be the equivalent of their heart beating 1 billion times.
The rate at which a mammal’s heart beats is relates to the animal's size in an inverse way, which means that the greater the body mass the slower the heart rate will be. For example, an elephant’s heart beats very slowly in comparison to a mouse. The average life span of an elephant is around seventy years whereas a mouse will only live for a couple of years, yet their hearts will have beaten a similar number of times by the time they die.
As animals get bigger, from tiny shrew to huge blue whale, pulse rates slow down and life spans stretch out longer in tandem, so that the number of heartbeats during an average stay on Earth tends to be roughly the same - i.e. about a billion.
There are of course other factors that will effect the longevity (the life span) of a particular animal, such as disease and environmen, but scientists have found that mammals in the wild will indeed live for about the time that it takes their heart to beat 1 billion times.
In 1945 Brody originated the term Physiological time to indicate that smaller animals seem to live according to a faster time scale than large animals.
The content on this site has been drawn from a wide range of Web & printed resources and edited/summarised to form a single point of reference and overview of the Billion Heart Beats.