elephant and mouse
Credit: Pixabay/CC0 Public Domain

Astronomers peering through telescopes at distant galaxies, or experimenters smashing particles to smithereens, are some of the things physicists think of when they think of unraveling the mysteries of the universe.

We also tend to reach for physics when biologists try to understand life. The new research shows that physics may not always answer questions of biology.

Scientists have been asking why large animals burn less energy and need less food. An enormous baleen whale can get by on a daily diet of just 5- 30% of its body weight in krill, while a tiny shrew needs to eat three times its body weight in food each day.

Previous attempts to explain the relationship have relied on geometry and physics. This relationship allows an animal to produce offspring.

Life is shaped by physical constraints.

Nearly 200 years ago, the earliest explanation for the disproportionate relationship between metabolism and size was presented.

French scientists argued in the 19th century that energy metabolism should scale with the surface area. The amount of heat an animal can excrete depends on its surface area.

There are many alternative explanations for the observed scaling of metabolism.

The most famous of these was written by US researchers in 1997. They came up with a model for describing the physical transport of essential materials.

They said their model offered a basis for understanding the central role of body size in all aspects of biology.

Both models are similar. They attempt to explain biological patterns by using physical and geometric constraints.

Evolution is able to find a way to work.

The laws of physics can't be broken by living organisms. Evolution has been able to find ways to overcome constraints.

We decided to look at the relationship between metabolism and size if we ignored the constraints.

We created a model of how animals use energy over the course of their lives. In our model, animals devote energy to growth early in their lives and then to reproduction later in life.

From an evolutionary point of view reproduction is the main game and we used the model to figure out what characteristics of animals result in the greatest amount of reproduction over their lifetimes.

The animals that are predicted to be the most successful at reproducing are those that have a disproportionate scale of metabolism.

disproportionate metabolic scaling is not the result of physical or geometric constraints. Natural selection makes this scaling because it's good for reproduction.

The wilderness has never been explored.

Nothing makes sense in biology except in the light of evolution according to Theodosius Dobzhansky.

disproportionate scaling of metabolism can arise even without physical constraints, suggesting we have been looking in the wrong place for explanations.

It has been thought that physical constraints are the main driver of biological patterns. There are more possibilities than we realize.

We've historically been willing to use physical constraints to explain biology. Maybe it's because we're more comfortable in the safe refuge of seemingly universal physical explanations than in the biological wilderness of evolutionary explanations.

Under a Creative Commons license, this article is re-posted. The original article is worth a read.