Let us begin with a definition of biological evolution (the term can be applied to other areas of change).  It is the change in populations of organisms through time.
    First of all, trying to prove evolution is not something scientists spend time thinking about or doing.  That was accomplished in 1859 when Darwin published his book “Origin of Species” and nothing has been presented since then to cast any doubt.  Having said that, the process of evolution is extremely interesting and absorbs a lot of scientific time and effort.  And, having said that, I have spent almost my entire life immersed in science and associating with scientists, some devoutly religious and some profoundly areligious and most falling somewhere in between but in no case can I recall meeting a scientist that was against individuals practicing a religion of their choice.  In short, acknowledging that being an evolutionist does not mean a person must be an atheist or agnostic.
    Can you think of one thing in this universe that does not change?  Even the most durable materials are affected by bombardment of high energy particles.  Why should we think that life, the most dynamic aspect of earth be exempt?
    The same process of science that brought us a sun centered solar system, a spherical earth, atomic theory and miracle cures is the process that brought us the theory of evolution.  All of these help us to explain our universe and to make predictions.  Are they true?  Only time will tell. 
    Science can change with the presentation of new evidence and ideas with better explanatory powers.  At one time, heredity was thought to be the result of “pangenes” present in the blood.  With Mendel’s mathematical approach to inheritance, the pangenes didn’t “pan” out.  Chromosomes seemed to follow Mendel’s mathematical explanation so they were thought to be the source of inheritance.  Chromosomes were analyzed and found to be made up of proteins and nucleic acids.  Which one would be the better “code” for inheritance?  Obviously proteins (a linear code with up to 20 different amino acids could code for a heck of a lot of things).  Nucleotides come in only four varieties and could obviously code for far fewer things.  In 1953, the structure of DNA was solved and its code deciphered.  James Watson and Francis Crick determined the structure of the deoxyribonucleic acid molecule and broke the three nucleotide code that serves to assemble proteins from amino acids.  Who today doubts that nucleic acids are the key to inheritance?  And, yet, who has even seen a nucleotide?
    Science is a process and if new evidence is presented that contradicts then we must re-think our conclusions.  All of us in science have our cherished beliefs (gravity pulls toward the center of the earth, DNA is the hereditary material, the earth is very old, current life on earth evolved from pre-existing life, etc.).  However, we can all envision a scenario that if evidence proved to be true, we would have to give up our cherished beliefs).  That is to say, science is tentative!
    Joseph McInerney said that science is not a democratic domain, and its principles are not subject to vote.  Raise you hands if you want gold to have an atomic weight of 16!
    There are two questions to be asked about the history of life on earth:
    1.    What happened?
    2.    How did it happen?

“What happened?”
    This is the easy question and its solution is no different than assembling a jigsaw puzzle.  Fossils.  Fossils are the evidence or remains of past life.  Oklahoma is known throughout the world for its fossils.  People come from far and wide to study our fossils and our stratigraphy.
    Fossils clearly tell us that life has been on earth for a very long time and that the forms of life have changed.  The earliest fossils are of pretty simple life forms.  Cellular complexity and organismic complexity came much later.  Once complexity reached the organ/system level over a half-billion years ago, complexity seemed to have run into a “barrier.”  That is, complexity has stalled out and the most complex organisms of today aren’t any more complex than those of the Paleozoic Era.  Different, but not more complex.  Also, many less complex (simple) forms of life are still with us and evolving right along with the complex life forms.  In fact, it can be argued that the simple forms of life have always dominated earth and always will.  What I am trying to say is that the fossil record does not show a linear process always going toward more and more complexity or “perfection.”  It shows a rather chaotic maelstrom of change in one direction, followed by extinctions, succeeded by great expansion of another form of life only to be replaced by something else that gets its “fifteen minutes of fame.”  Understanding the fossils and trying to put this part of the puzzle together falls under the realm of paleontology.
    Stratigraphy on the other hand is the science of making sense of the order of events.  This is based on the continuous process of erosion and deposition that constantly remodels the earth’s surface.  The layers created by deposition are called strata and “reading” the strata is about like scattering the numbered pages of a book along a stretch of road.  It makes reading the book more difficult but as long as the pages are there and numbered, it can still be done.  

“How did it happen?”
    This is the hard question to answer and the one that scientists have been debating since Darwin’s time.  Charles Darwin did not invent the concept of evolution.  The idea had been around for some time before he was even born.  In fact, when he embarked on his famous voyage he was a creationist with a university degree in theology, prepared to be a minister in the Church of England.  What he observed on the voyage eventually brought him to conclude that organisms indeed do evolve from pre-existing organisms.  What he called “descent with modification.”  Eventually he came to the decision (as did others) that the mechanism for that change was natural selection and natural selection was based on these three premises:
1.     Overproduction – the reproductive potential of all organisms can potentially outstrip their food, space or other resources.
2.    Individual Variation – many traits within populations are variable.  This has been known for many years and demonstrated with crude measurements but has really come to the forefront recently with DNA “fingerprinting.”
3.    Differential Reproductive Success – Individuals with favorable combinations of genes (i.e. traits) will contribute more to succeeding generations.  Conversely, individuals with unfavorable combinations of genes (i.e. traits) will contribute less to succeeding generations.  Mathematically this will result in a shift in gene combinations that are most adaptive to the environment in which the organism exists.  If the environment changes then natural selection will act on the population to shift the genetic make-up.  Or, if the gene pool isn’t adequate to make the shift, then the population may be unable to adapt and face extinction. 
That is natural selection in a nutshell.  It is difficult to imagine any
argument against any of those three premises.  It seems to be a major driving force in the process of evolution.  How important is it?  That is difficult to say and certainly brings a great deal of debate among scientists.
    What other evolutionary forces are at work?  Well, sexual selection is another factor at least among some sexually reproducing organisms.  Males and females may be able to behaviorally or physiologically select what individuals with which they wish to exchange gametes.  Sometimes the more outlandish the opposite sex, the more attractive.  Thus we end up with garish colors, overwhelming antlers or bazaar behavioral antics.
    There are many other processes that have been identified such as: the founder principle, the bottleneck effect, stabilizing selection, disruptive selection, polyploidy, non-disjunction, etc. etc.  However, even all these together can’t explain all of evolution.  There is still a lot to learn and in a hundred years the theory of evolution may look a lot different than it does now.  However, nothing will change the fact of evolution as demonstrated by the fossil record.  What will change is our understanding of the pattern of evolution through the discovery of new fossils and the process of evolution through observation, experimentation and dialogue.

This article was published in: Crosstimbers: A Multicultural, Interdisciplinary Journal, Spring/Summer 2005 (Chickasha: University of Science and Arts of Oklahoma. 2005), 23-25.

                                                                                     "Sue" -- greeting visitors


                                                                                                 "Sue" -- another view

                                                        180 million year-old ammonites I purchased in 1972 in Switzerland