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evolution, science

Evolutionary Arms Races


There are two primary kinds of evolutionary “arms races” — symmetric and asymmetric.  A symmetric arms race is one in which two or more competitors are trying to do essentially the same thing.  If we imagine a forest full of various trees, vines, and other plants, we can easily see this kind of arms race in action.  All of the trees, regardless of their particular species, are interested in the same thing, namely sunlight.  To that end, many of them “discover” the same path to their goal.

Imagine a primordial forest in which (for simplicity’s sake) there is one kind of tree that grows to approximately ten feet in height.  So long as all the trees grow to the same height, everything will be stable, but the fact is, natural selection produces variation, so sooner or later, one of the trees is going to grow to eleven feet.  Let’s assume that this tree has an umbrella like spread of leaves at the top, so that ten foot trees will receive less sunlight if an eleven foot tree is next to them.  In a very few generations, eleven foot trees will dominate the landscape.

Only… natural selection produces variation, so soon, there will be a twelve foot tree.  This is the nature of symmetrical arms races, and individual species are one of the best examples.  All members of a species are competing for the same thing, and so they tend to push each other towards new innovations.  Once we understand this dynamic, it’s easy to see that different species also have the same effect on each other.  Elms and oaks and pines all want the same thing, and so they tend to evolve in very similar ways.  Though elms, pines and oaks don’t have precisely the same leaf shape or root structure, they are still in the same business — getting to the sunlight and absorbing it through leaves.   They’re all part of the same arms race.

An asymmetrical arms race is one in which the goals of two or more participants are mutually exclusive.  That is, success for one is necessarily failure for the other.  This is the kind of relationship we see in predators and prey.  The lion wants to kill and eat the gazelle.  The gazelle wants to avoid being eaten by the lion.  For one to achieve its goal, the other must fail.

In a symmetrical arms race, we often see multiple species achieve their ends through very similar innovations.  In the case of trees, it is largely a matter of height.  In asymmetrical races, we tend to see much more dynamic and intricate solutions.  For many insects, for instance, a highly elaborate system of mimicry or camouflage develops to counter the highly elaborate system of detection posessed by predators such as bats and birds.   It is not unlike the arms race in which humans developed radar to detect airplanes, and then promptly developed airplanes with radar defeating countermeasures.  One innovation prompts the development of another.

These examples are very simple, and are meant only to illustrate the broad principles.  What we must remember is that most, if not all, natural arms races are not as simple as these one against one examples.  In the real world, gazelles must not only avoid lions.  They must also avoid hyenas, who have entirely different hunting strategies.  They must also avoid starvation, dehydration, and disease.  They must compete with each other for mates.  In short, there are dozens, maybe hundreds of individual arms races going on at any moment, and every creature is in effect a compromise between all of the races going on.

Even so, there is much we can learn by examining the results of arms races.  Let’s return to the trees as an easy example.  Just how far will natural selection drive trees?  Left unmolested, would forests be populated by 5,000 foot trees in a billion years?  No, they wouldn’t.  Arms races are not infinite.  There are real physical limitations to how tall trees can grow.  Wood is only strong enough to hold a certain weight.  Gravity opposes the absorption of water through the roots.  Wind tends to knock down trees that are too tall for their own good.  Eventually, arms races will stagnate because there is simply nothing left to improve.   (Of course, this is also overly simplistic, as height is not the only trait available for an arms race.)

At this point, we should see a certain principle of natural selection that seems counterintuitive to a lot of people.  Evolution is not very good at efficiency.  There is a finite amount of sunlight hitting the trees, and if competition is forcing them to grow ever taller to get to it, the net result is that trees are getting less bang for their buck.  A ten foot tree only has to support ten feet of trunk whereas a fifty foot tree has five times as much trunk to support while using exactly the same amount of sunlight.

A better solution would be for trees to form some sort of pact by which all trees would grow to ten feet and then stop so that all could benefit from both the sunlight and the efficiency of being small.  We can now ask a very pointed question.  If life is intelligently designed, how did the designer miss such an obvious arrangement?  Rather than design life to strive for less efficient use of energy, why not design it such that it would reach a state of most efficient use of energy and then stay there?

Granted, this isn’t really much of an argument.  It’s an observation that raises a question.  Still, it’s something I’ve never heard addressed by a proponent of intelligent design.  It’s a very logical question to ask, anyway.

There’s one more observation I’d like to make about this tendency towards arms races and inefficiency.  It works for humans, too.  Take a look at the world around you and look at how much energy it takes to sustain a human.  Now, compare that to a hundred or five hundred years ago.  Sure, we have a lot more gadgets and gizmos than we did before, but it takes a LOT more energy to sustain a human now than it used to.  We are not moving towards efficiency, but away from it.

To head off the most obvious objection to this observation, I will note that efficiency within a particular system is not the same as overall efficiency.  That is, if we build cars that get fifty miles per gallon as opposed to twenty, that is certainly making more efficient use of energy within that particular system.  However, the overall trend in humanity is not to use less energy, but to be able to do more things with the energy we have, and to produce more energy overall so that we can do more things overall.

Looking back over the history of life, it is telling that only in the last few thousand years (or less) have humans even been able to comprehend the question of efficient energy use and devise ways to produce the same amount of work for less energy.  Only in the past century have we become keenly aware of the horrific consequences of using too much energy too fast.  Isn’t it odd that even with this knowledge, we are still travelling down a path predicted by the simple formula from natural selection?  We are still competing with each other, still using more and more energy to accomplish more and more things despite having learned to use science to make our energy expenditures more efficient.  No, I don’t think it’s a very intelligently designed system at all.  In fact, I’d say that the only thing that might save us from the illogic of the system itself is to collectively rise above instinct and learn to reduce our competition and increase our efficiency.  Unlike trees, we do have the power to make collective bargains, and we can decide that ten feet is tall enough.

Will we do it?  I don’t know.  I tend to think not.  Our instincts are strong, and we are not designed to be collectively logical.  Sometimes I wish there was any evidence at all that someone with some intelligence designed this planet.  Natural selection is elegant and explains life as we know it with virtual perfection.  We know it’s the correct answer.  However, it’s very telling that we can also use our own logical minds to realize that it’s not designed for our happiness or longevity.  It doesn’t have enough forethought for that.



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