Recently I’ve been wearing one of those heart rate watches to the gym. 

It’s actually pretty fun to develop a feel for when my heart rate is at 120 beats per minute or at 160, or is spiking at 180 (I try not to go above that).  For most of us, our average heart rate is 70-75 bpm.

My brother forwarded me an interesting chart which shows how human bpms compare to other animals.  As the downward sloping line in the chart on the left shows, there’s typically a pretty good (inverse) link between bpms and life expectancy (if bpms are high, then life expectancy is low). [Note: I’m not sure why they have “whale” listed twice on this chart.]

What’s really interesting to see is where “Man” falls.  Given our bpms, we should be with tigers and giraffes who have a life expectancy of ~20 years.  And in the Neolithic era 5-10 thousand years ago, human life expectancy actually was 20 years.

But today the average American lives 4 times as long as this, on average 78 years (as of 2008).  Diet, medicine, technology, etc have all boosted our life expectancy to extraordinary degrees.

The chart on the right is interesting too, mainly because its display greatly undersells the number of extra beats humans get — because the chart’s scale is exponential.  10 to the 9th power is 1 billion; 10 to the 10th power is 10 billion.  That 9 billion difference is a pretty big one for such a little shift to the right!  For humans, we’re about 10 to the 9.4th power, which is 2.5 billion beats over our lifetimes, or about 80 years.

So next time you’re at the gym, you can be thankful that after exercising, your heart rate will settle back down to a much more sustainable level!