Monday, April 20, 2015

Another Evolution Analogy

In a previous post I discussed (among other things) Richard Dawkins' "Climbing Mount Improbable," in which he laid out a good analogy comparing the gradual process of evolution to a walk up a very gradual slope that eventually leads to the top of a very high mountain.  It's a very good analogy, but I fear it may require a bit too much work to accept it since (a) not everybody has experience with climbing up gradual slopes and (b) a change in altitude is not really in the same conceptual ballpark as the change that species undergo over time.  It's strength is, I believe, primarily in the way it conveys how extremely small changes can add up to large changes over extreme lengths of time.  But some folks will probably still reject it because they simply can't get their minds wrapped around the comparison of time to distance.

After much thought, I believe I have come up with, if not a better analogy, at least a complimentary analogy to the one Professor Dawkins discussed.  It lacks the sense of vast time in Dawkins' analogy, but is more grounded in everyday experience and deals with actual biological processes.  It also helps deal with the common objection heard by Creationists that there are no "transitional" fossils that show one species evolving into a completely different species.

Let's imagine a father who photographs his newborn child and decides to take a new photograph of the child once every minute of every hour of every single day from that point on. At the end of the first day, the father has 1400 pictures, after one week he has 10,080 pictures, and at the end of a year he has a whopping 525,960 pictures. At the end of ten years, the stack has grown to 5,259,600 pictures, and by the time the child is 50 years old, the stack has grown to 26,298,000 pictures. And (assuming the father was extremely long-lived or passed the duties on to somebody else), by the time the child is 90 years old, the stack has a massive 47,336,400 pictures, all showing the gradual growth of a baby into an elderly man one minute at a time.

Now, over a period of ninety years, the child has changed from a newborn infant to an elderly man, and along the way the child progressed through various well-defined stages (infant, toddler, child, pre-teen, adolescent, young adult, adult, middle-age, senior citizen, elderly) . And if you randomly selected any example from that stack of 47,336,400 pictures, you would be able to clearly identify which stage of life the child was in at the time that photograph was taken. No photograph, however, would show a clear "transition" from one stage to the next. You wouldn't, for example, find a picture showing the child with the body of a baby and the head of a toddler. Or the arms of a teenager but the legs of an adult. Or (to mirror some of the extreme examples asked for by Young Earth Creationists), the body of an infant and the head of a senior citizen.

The point is that the change from infant to elder is so gradual that there are no clear-cut transitions from one stage of life to the next. Somebody may legally be considered an adult at the age of 18, but it would be impossible to detect any physiological differences between a person one minute or one hour or even day before his 18th birthday and one minute, hour or day after his 18th birthday. And this isn't to say that there aren't any transitional photographs of the child; instead, it means that every single photograph shows a transition from the previous minute to the next minute and the supposedly "well-defined" stages of life are really just shortcuts we use to describe people instead of actually having some sort of absolute definitions.

The same is generally true with regard to the fossil record and the evidence it provides for evolutionary processes.  Just as children gradually change into adults over time, species gradually change into other species over time.  The only difference is that species change over millions of years instead of 90 years, but the principal is the same.  Just as you will never find a photograph of somebody who has the head of an infant and the body of an adult, you will never find a fossil showing the head of one species and the body of a previous species.  And this isn't to say that there aren't any transitional fossils; instead, it means that every single fossil shows a transition from the prior generation to the following generation and the concept of "well-defined" species is really just a shortcut we use to describe life instead of actually having some sort of absolute definition.

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