Life appears to require at least some instability. This fact should be considered a biological universality, proposes University of Southern California molecular biologist John Tower.
Biological laws are thought to be rare and describe patterns or organizing principles that appear to be generally ubiquitous. While they can be squishier than the absolutes of math or physics, such rules in biology nevertheless help us better understand the complex processes that govern life.
Most examples we've found so far seem to concern themselves with the conservation of materials or energy, and therefore life's tendency towards stability.
For instance, Allen's rule, formulated in 1877, states warm-blooded animals in colder areas require stouter limbs with less surface area to conserve body heat, whereas in warmer regions the opposite is true. But as with everything biological, there are some exceptions: including short-legged bush dogs found in Central and South America, and the common frog.
Another example of biological 'rules' lies in repeating structures that obey mathematical power laws as they increase in size, such as the ever-expanding spiral of a nautilus shell. These are widespread across many biological systems and again are strategies believed to conserve the use of energy and material. The way bees make hexagonal honeycomb is another clever example.
"Self-similar structures, including logarithmic spirals, are thought to be the most economical way to grow the size of a structure, without changing shape or destroying existing structure," explains Tower.
His concept, termed 'selectively advantageous instability', however, challenges this tendency towards the conservation of resources in biological systems.
It claims at least some volatility is a fundamental biological necessity, despite such instability leading to the loss of resources. That's because there are other things to gain.
"Selectively advantageous instability increases the complexity of the system, and this increased complexity has potential benefits," Tower writes. These benefits include the power to change and therefore adapt, which occurs across all biological levels from the molecular to population.
"Even the simplest cells contain proteases and nucleases and regularly degrade and replace their proteins and RNAs, indicating that selectively advantageous instability is essential for life," Tower says.
The requirement of instability inevitably leads to a loss of energy and resources, and the accumulation of genetic mutations that may be either harmful or benign. This is how we end up with biological aging, Tower speculates.
Yet without instability and its downsides, life wouldn't be able to adapt and flourish through changing time and space.
So we're all caught in a contradictory tug of war between a need for stability and instability, making compromises either way.
"Science has been fascinated lately with concepts such as chaos theory, criticality, Turing patterns and 'cellular consciousness," says Tower.
"Research in the field suggests that selectively advantageous instability plays an important role in producing each of these phenomena."
This research was published in Frontiers in Aging.