3 min read
When you look around at the diversity of life—from the smallest bacterium to the largest mammal—on the surface, there would seem to be little that unifies it all.
I find comfort in the notion that there’s a unity, an underlying formula, that connects me to surrounding life, whether it’s the blades of grass below my feet or the wild deer that prance upon them.
-Dr. Jason Holland, Lifespark
Referred to as Kleiber’s law, for Dr. Max Kleiber and his work in the 1930’s, this formula shows that across different species there is a rather precise relationship that exists between an animal’s weight and metabolic rate.
Compare a common house cat to a jaguar as an example. The jaguar is about 30 times as massive. So, you might then naively assume that it would produce 30 times as much energy. But that isn’t the case.
Even though a jaguar has approximately 30 times as many cells, it would on average only produce about 13 times as much energy as a house cat. That’s because Kleiber’s law states that an animal’s metabolic rate scales to the ¾ power of its weight (e.g., for this example, you’d multiply 30 by itself 3 times and then take the square root twice).
Over the past two decades, Dr. West has significantly expanded on Kleiber’s work and demonstrated the ubiquity of ‘quarter-power scaling laws’ (e.g., scaling at an exponential rate of ¼ or ¾) in predicting a range of biological processes across diverse kinds of plants and animals.
As he explains in his 2017 book, Scale, “similar scaling laws hold for essentially all physiological quantities and life-history events, including growth rate, heart rate, evolutionary rate…life span, the height of trees and even the number of their leaves.”
One extension of these laws is that, although there’s tremendous variation in pulse rate among different species, most creatures are, more or less, constrained to the same maximum number of beats in a lifetime. That amounts to about a billion and a half beats.
But that, of course, doesn’t mean that we’re all marching to the same beat. As West explains in his book, “Small creatures live life in the fast lane while large ones move ponderously, though more efficiently, through life; think of a scurrying mouse relative to a sauntering elephant.”
Thus, we live in a scale-dependent universe. And perceptions of time and space on a human scale represent only one narrow plane of experience.
Such a realization is both humbling and exhilarating. It’s humbling because our experience is so limited and exhilarating because there’s so much beyond our human senses that we have yet to learn.
But above all else, when I think about West’s findings, I find comfort in the notion that there’s a unity, an underlying formula, that connects me to surrounding life, whether it’s the blades of grass below my feet or the wild deer that prance upon them.
What are your thoughts and reactions to Dr. West’s work? Let us know in the comments below.