A biology professor explains what fish can teach humans about geopolitics

Nature has been hiding itself in plain sight for a lot longer than humans have.
Nature has been hiding itself in plain sight for a lot longer than humans have.
Image: Molly Cummings/Erich Schlegel
We may earn a commission from links on this page.

While we humans ponder escalating arms races at times when tempers flare across oceans and neighborhood fences, nature has to worry about it 24/7.

We can learn some expert tricks for dealing with unseen threats from nature’s masters. The difference between the natural world’s full-time preoccupation with life-threatening matters versus our part-time devotion is that while we have the option of turning off or tuning out, the Earth has had to develop some impressive coping mechanisms.

Take, for example, the underwater battle that has been playing out between animals living in the ocean for millions of years. One group of predatory animals wants to find prey in the vast waters, while the species being preyed on are desperate to go undetected. But how do these prey avoid detection when they come into close range with their predators? Or, in humans’ case, when your rival nation can use satellites to locate you and your assets, how do you avoid bobbing about, sticking out like a gray whale against the water’s surface?

In a war between rivals, one response to a threat of an attack is to run and hide. But hiding in the open seas is not an easy task. It’s a featureless place with no walls to hide behind, forests to retreat within, or rocks and sand to blend against. Instead, you only have water—and lots of it. Most prey faced with this dilemma have therefore resorted to a form of a watery camouflage to blend into the medium itself. (And, if that doesn’t work, swim away as fast as you can.)

At first, blending into the water’s background may have been simple. If your predator can see only color and intensity of light, then the evolution of mirror-like skin might solve the problem. If the watery world to the left of you appears the same in brightness and color as it does on the right, then mirrors are an easy trick to fool your predators of your presence.

However, as with every arms race, duels between parties can escalate quickly. In the case of detecting prey objects in a seemingly featureless place, many fish species having taken their visual systems up a notch by evolving detectors that are capable of seeing features even our human eyes cannot. For example, they see polarized light, which transforms their watery world into one with a kaleidoscope of backgrounds. Now instead of having a seascape that appears homogenous all around you, these fish can see differences in the polarized light field as it varies by angle and degree with respect to the sun.

That’s great for the predators—but not so great for the prey. This now means that instead of having a single background to match at any given time, prey species now have an extremely challenging hurdle of matching an array of polarized backgrounds that change throughout the day.

Sounds like an almost impossible natural design task, no? It certainly does seem daunting, but never underestimate the power of nature to find a solution when the need is in high demand. There are some open-ocean fish that have come a long way in solving that mind-boggling task of camouflaging against a dynamically polarized background. And how they do it is quite ingenious.

A representation of the invisibility effect of the jacks’ scales.
A representation of the invisibility effect of the jacks’ scales.
Image: Molly Cummings/Brady et al. Science 2015

These open-ocean-dwelling fish belong to the family of jacks known as the carangids, and they have two different layers of specialized reflecting cells called iridophores. One of these cell layers acts very similarly to a mirror, helping the fish match the change in light intensity in the vertical plane (as light above is always brighter than light below in the ocean). Meanwhile, the other layer of iridophores has a very specific orientation to accommodate the ever-changing polarization characteristics that circumnavigate the fish in the horizontal plane. This divide-and-conquer strategy allows the carangids’ skin to blend into their watery world from whichever direction a predator may approach.

The jacks’ specialized skin features are an evolutionary adaptation to their specific environment. Given that fish have been swimming the seas for millions of years longer than humans have waged wars, maybe there’s something to learn from them.

We could benefit from becoming more aware of all the dimensions our world contains. It is rich with complexities that change with our individual perspectives, and a single solution does not fit all challenges. Instead, we need to adjust our approach to address the multidimensional features of each environment. By doing so, we will be able to find the ultimate solution for every given situation instead of floating through the open seas, hoping we don’t swim into the open mouth of our predators.