In his book "Scale", Geoffrey West, takes a close look at Biology using the physics toolbox and finds fascinating patterns. Did you know that the hearts of all mammals beat approximately 1.5 billion times? The heart beat rate gets slower as the weight of the animal grows, with heavier animals therefore living correspondingly longer. According to the data compiled in the book, this rule also applied to us, homo sapiens, up to about 1800. Thanks to the technological and societal improvements, our hearts now beat 2.5 billion times on average.

A second finding was that all mammals consume approximately 300 food calories per gram of body mass throughout their entire lifespan. This was also true for us humans before we started agriculture, and our energy flux corresponded to about 100 watts. Since then, it has grown to about 11'000 watts, almost as much as that of a whale.

Suppose unconstrained Darwinian evolution were the only mechanism at play then we would not expect to see "constants" like the one's above. We would see a continuum of values. It was this discrepancy that led West to the research and the findings published in the book that I am not going to leak here, of course.