Who are the Winners in this Race?

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“My dear, here we must run as fast as we can, just to stay in place. And if you wish to go anywhere, you must run twice as fast as that”

These lines, taken from the well-known fantasy novel “Alice’s Adventures in Wonderland” by Lewis Carroll, aptly summarize the struggle and race for survival of species in this world. When most of us think of survival and evolution, Darwin’s famous words come to mind: ‘Survival of the fittest’. What exactly do these words mean?

If we lived in the wild, lacking all the comforts we have in today’s world, we fall under one of two categories: predator or prey. In a way, ALL living organisms fight in this constant battle on one side or the other, the loss of which results in the loss of life and ultimately the extinction of a species. The prey runs from the predator, and the predator runs after the prey. The prey in turn predates and runs after some other organism. So in a way this makes running a crucial part of our lives, an important part of survival. In the end, life is a constant race, and everything boils down to who runs faster.

            I am reminded of another famous line, this time from Aesop’s fables –

"The rabbit runs faster than the fox, because the rabbit is running for his life while the fox is only running for his dinner."

Here we understand that the prey has to constantly evolve to be fastest, stronger and smarter to outrun its predator, in order to just stay alive and therefore not go extinct. Does this mean that evolutionary selection pressure operates only on prey species and they keep evolving into swifter species? Do the older, slower species die out, constantly replaced by newer, faster species? This cannot possibly be true for only the prey species. The fox cannot afford to miss its dinner each time as this surely means death; it simply has to run faster and learn new tricks to outwit the rabbit.  

Mortal enemies in Nature are in a never-ending arms race; better capabilities in one necessitate compensatory changes and innovations by its enemies if they have to win, stay alive. The weapons used in this war are characters or traits (physical or physiological) which are selected throughout evolution and which determine the outcome of all conflicts. These traits are honed to perfection after generations of interactions with each other. One favourable change in one species which gives it an edge in survival will force a reciprocal change in its enemy, and so on and so forth with both the players running neck to neck. One step forward by one obliges the other to move a step ahead.  

The degree to which players in the arms race respond to each other can be explained by two theories, symmetrical and asymmetrical evolution of prey and predator. In simple words, does evolution in one group result in an equivalent evolution of the other? Like many questions in science, this one too has two answers, yes (symmetrical evolution/ co-evolution) or no (asymmetrical evolution/ escalation). As explained above, co-evolution means both the players evolve together in response to each other’s adaptation.

However the other more plausible explanation, especially for predator-prey interactions, which also may be more accurate, is escalation or asymmetrical evolution. Characters which help the prey (which is running for its life) survive mostly evolve in response to the predator; however there is little proof that the prey drives a counter-adaptation in the predator (which is running only for its dinner). It is more likely that the changes in predators are driven by their own predators or competitors.

Another reason for the asymmetry in evolution would be the level of intimacy with which enemies engage with each other. A predator which fails to detect a hidden prey or loses in a chase does not interact physically with the prey and so avoids many defence mechanisms of a prey like toxins, sharp spines, etc. It only loses its meal and whatever energy was used during the chase.

Predators also are mostly generalists – which means they are opportunistic and feed on a large number of prey species. This gives the predator several chances to change its prey if one becomes rare or difficult to catch. The ability to feed on several species also lessens the selection pressure on the predator. On the other hand, a predator which specialises on hunting a particular prey would be forced to constantly co-evolve with the prey to survive.

All the explanations given above are oversimplifications of the myriad of interactions between the millions of organisms around us and the ingenious mechanisms they have developed to deal with each other. We should observe carefully and try to understand these interactions before all players are wiped off the arena – prey to the super-predator, MAN.

 

With invaluable inputs from my son, Dhananjay.

Reference –

Edmund D. Brodie, III, Edmund D. Brodie, Jr. (1999) Predator-Prey Arms Races: Asymmetrical selection on predators and prey may be reduced when prey are dangerous, BioScience, Volume 49, Issue 7, Pages 557–568, https://doi.org/10.2307/1313476

Additional reading – Please browse the internet for examples of species adaptations. 

 

Article by:

Dr. P Anuradha Reddy

Scientist, Laboratory for Conservation of Endangered Species (LaCONES)

Centre for Cellular and Molecular Biology (CSIR-CCMB), Annexe I

Hyderabad 500048