Tuesday, January 28, 2014

A LAYMAN’S EXPLANATION OF EVOLUTION

A comment my daughter Michelle made on a Facebook thread recently got me thinking about the concept of evolution.  She pointed out that evolution is nothing more than the natural outcome of a few basic principles of biology and that there is really nothing “theoretical” about it.  She was stating that evolution is simply the result of the operation of those basic principles and to call it a “theory” is like speaking about a “theory” of square.  Through the operation of a few basic principles of biology, on which we all should agree, evolution happens in the same way that following a few basic operations in geometry results in a square.

I am no biologist.  In fact, although I have had a great affection for science my entire life, I was always least comfortable with biology.  But I am hoping that that might give me an advantage in explaining evolution as a true layman.


So what are the biological principles that result in evolution?  If I had to list them, they would include the following:

1. Limited Lifespan.  Individuals of a species have a limited lifespan.  It might be fun to speculate about a world where organisms have unlimited lifespans.  (Maybe there’s a science fiction plot lurking in there somewhere.)  I suppose that such organisms would need to have self-repair mechanisms to cover accidents or other adversities.  If such organisms gave rise to progeny, then, unless the older generation eventually died off, the environment would ultimately get overcrowded and the ensuing competition would result in some individuals getting “crowded out.”  So I think such a scenario would come down to the same result.

2. Progeny.  Given that individuals of a species have a limited lifespan, if they didn’t produce progeny, then the species would eventually die out.  And of course that’s the story behind virtually every extinct species.  Those species that, for whatever reason, don’t produce enough progeny to carry on the species are simply no longer around.  And that has been the case with nearly all species over time.  Estimates are that 99.9% of all species that have existed are now extinct.  But during the existence of a species that is producing progeny those progeny carry on the genome of their parents.  In Darwin’s time this genetic mechanism was not understood, but what was understood was that the progeny of a species did inherit nearly all of the characteristics of their parents.

3. Variation.  Biologists in Darwin’s day also observed that while the progeny were very similar to their parents, there were individual differences.  Those differences could seem minor and inconsequential--the young of a leopard had spots but those spots might be smaller or larger or with a slightly different coloration than the parents’ spots.  Or the differences might seem more important--a leopard born with less or more prominent canine teeth, for example.  Again, biologists at the time didn’t understand why there were individual differences, but they were able to observe that those differences were inheritable by the progeny’s offspring.

4. Competition.  And here is where Darwin’s genius came in.  He realized that such variations put the progeny at an advantage or disadvantage in their environment and that that advantage or disadvantage could be measured by the number of progeny they produced that, in turn, had progeny to carry on that inherited characteristic.  Those variations that put the individual at a competitive advantage resulted in more progeny; those that put the individual at a competitive disadvantage resulted in fewer progeny.  It’s as simple as that.  

5. Definition of Success.  It is important to point out that evolutionary success has nothing to do with “improving” a characteristic as such.  The fact that we have large brains is not a measure of our success as a species.  The only evolutionary measure of success is based on how well a species does in propagating its genome.  And even that is misleading.  The biology of evolutionary processes is not goal-driven.  There is no teleological goal that the biological processes are striving for.  It is not that a genetic trait is implemented in order to make the species more successful in terms of generating progeny.  Rather, a genetic trait either results in more offspring or it doesn’t.

6. Time.  Evolutionary processes generally take time, quite a bit of it actually.  In most cases the changes that a species undergoes are gradual.  This isn’t always the case.  There may be drastic environmental changes that deny nearly all the current members of the species the ability to produce offspring that could carry on the genome and only those members who possess a rare genetic trait are able to survive and produce progeny. But for the most part the changes to a species are gradual and may occur only over a considerable number of generations.  Though, keep this in mind: The evolutionary changes in a species’ traits can and do occur concurrently.  Birds of prey, for example, did not first evolve feathers that allowed them to fly at great speed, followed by sharp talons, followed by keen eyesight.  Rather, all of these processes (and many, many others) were occurring at the same time.  Even so, the changes were gradual.  This may be a problem for young-earth creationists, who believe life on earth has only existed for a few thousand years, as most species, including humans, simply wouldn’t have had a sufficient number of generations for significant evolutionary processes to operate.  But that is not the biology community’s problem, it is the creationists’.  The fact is that all relevant scientific disciplines--geology, paleontology, microbiology, nuclear science, plate tectonics--corroborate the fact that life and evolutionary processes have been operating on the earth for literally billions of years. 

When I was first introduced to the concept of evolution, the ideas were so basic and so obvious that I wondered why I hadn’t figured it out on my own.  Of course, in fact it took decades for evolutionary principles to gain the overwhelming acceptance in the scientific community  that they have today.  But we know the reasons for that.  Simply put, it was the considerable threat to religious orthodoxy that evolution represented that delayed its acceptance.  

According to a 2012 poll (http://www.huffingtonpost.com/2012/06/05/americans-believe-in-creationism_n_1571127.html), 46 percent of Americans agreed with the following statement:  “God created human beings pretty much in their present form at one time within the last 10,000 years or so.”  If you find yourself in that number, I would ask that you review the six points that I have laid out and let me know which of them you disagree with.  If your reason for disagreement is based on scripture, then I would ask you to consider carefully the following: Which has been more successful in advancing knowledge over the past several hundred years, reliance on scientific investigation or reliance on the writings of pre-scientific authors who lived two to three thousand years ago?  In answering that question think geocentric vs. heliocentric solar system, think flat vs. spherical earth, think supernatural causes of earthquakes vs. plate tectonics, think all the other technological advances resulting from a rational, scientific investigation rather than reliance on scriptural revelation.  In the end I believe the answer is as easy as 1, 2, 3, 4, 5, 6.

© 2014 John M. Phillips


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