# How evolution shapes the geometries of life

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Why does a mouse's heart beat about the same number of times in its lifetime as an elephant's, although the mouse lives about a year, while an elephant sees 70 winters come and go? Why do small plants and animals mature faster than large ones? Why has nature chosen such radically different forms as the loose-limbed beauty of a flowering tree and the fearful symmetry of a tiger?

These questions have puzzled life scientists since ancient times. Now an interdisciplinary team of researchers from the University of Maryland and the University of Padua in Italy propose a thought-provoking answer based on a famous mathematical formula that has been accepted as true for generations, but never fully understood. In a paper published the week of Feb. 17, 2014 in the Proceedings of the National Academy of Sciences, the team offers a re-thinking of the formula known as Kleiber's Law. Seeing this formula as a mathematical expression of an evolutionary fact, the team suggests that plants' and animals' widely different forms evolved in parallel, as ideal ways to solve the problem of how to use energy efficiently.

If you studied biology in high school or college, odds are you memorized Kleiber's Law: metabolism equals mass to the three-quarter power. This formula, one of the few widely held tenets in biology, shows that as living things get larger, their metabolisms and their life spans increase at predictable rates. Named after the Swiss biologist Max Kleiber who formulated it in the 1930s, the law fits observations on everything from animals' energy intake to the number of young they bear. It's used to calculate the correct human dosage of a medicine tested on mice, among many other things.

But why does Kleiber's Law hold true? Generations of scientists have hunted unsuccessfully for a simple, convincing explanation. In this new paper, the researchers propose that the shapes of both plants and animals evolved in response to the same mathematical and physical principles. By working through the logic underlying Kleiber's mathematical formula, and applying it separately to the geometry of plants and animals, the team was able to explain decades worth of real-world observations.

Written By: Science Daily
continue to source article at sciencedaily.com

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1. This is cool. A while back I posted a comment wondering how sensible it was to look for a Grand Unified Theory for biology, something that unified all the various models we have into some more basic concepts such as energy, mass, information, etc. This looks like a step in that direction.

2. “fearful symmetry of a tiger?”

Not to be pedantic but should this read “fearSOME symmetry..”

3. Why has nature chosen such radically different forms as the loose-limbed beauty of a flowering tree and the fearful symmetry of a tiger?

Why has a writer chosen the word chosen to describe something that wasn’t a choice. This is the real question here.

4. The issue of heat dissipation in animals is interesting stuff. The Cheetah’s body temperature rises so dramatically with their awesome bursts of speed that they have to catch their prey in about 20 seconds or less or they overheat with potentially fatal consequences. Victorian cabbies were well versed with the fact that if they clipped a horse (read virtually shaved) and gave it high energy oats they got more work out of it for longer periods. The horses didn’t live too long.

5. In reply to #4 by aquilacane:

Why has nature chosen such radically different forms as the loose-limbed beauty of a flowering tree and the fearful symmetry of a tiger?

Why has a writer chosen the word chosen to describe something that wasn’t a choice. This is the real question here.

Laziness?

The author must know that natural selection has no goals or aims; that it’s the “cumulative non random survival of randomly varying self replicating information.”

It also jars with me when the word design is used within the context of evolution.

6. The writer of this article concludes that evolution is driven by physics and by math. Clearly evolution is being driven by the physical constraints. Math is just a tool to understand the constraints. Evolution is not being driven by math! Another addendum is the fact that animals have a nervous system. This too is driven by physical constraints. Animals have to avoid being eaten and they need energy by means of eating other plants and/or animals. This constraint of seeking food and avoiding becoming food is an interesting landscape which drives evolution to search for a “system” which can model the external environment and the internal environment as a representation. In this case, the nervous system provides a system of representation and the muscles provide locomotion. The added benefit is the blood which is also a coolant and large lung surface to dissipate the excess heat. Given the physical constraints, evolution has limited choices. Math has nothing to do with the whole affair. Math, like English, is just an abstract tool for our human understanding as we model the universe around us.