Thursday, March 09, 2006
Occam's Razor and "Populations Evolve, Individuals Do Not"
3) "Populations Evolve, Individuals Do Not"Several years ago I was talking about my interest in a testable internal evolutionary mechanism in some forum or other when someone came back with "Populations evolve - not individuals!". I had the distinct impression the individual concerned believed that this statement alone absolutely precluded the possible existence of any such mechanism.Individuals do not evolve, but if shared circumstances 'triggered' individual internal evolutionary mechanisms in a subset of a population then this could cause similar genetic changes to appear in their progeny. Thereby causing a "change in the frequency of alleles within a gene pool from one generation to the next."
"Evolution is a process that results in heritable changes in a population spread over many generations."
This is a good working scientific definition of evolution; one that can be used to distinguish between evolution and similar changes that are not evolution. Another common short definition of evolution can be found in many textbooks:
"In fact, evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to thenext."
- Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974
One can quibble about the accuracy of such a definition (and we have often quibbled on these newsgroups) but it also conveys the essence of what evolution really is. When biologists say that they have observed evolution, they mean that they have detected a change in the frequency of genes in a population.
And yet I could find little meaning in the statement. After all, I am not aware of anyone who has ever suggested an individual can evolve - and what exactly constitutes a "population"?
In the same (or a similar) discussion I asked "If a population consists of 'n' male/female pairs and I take one pair way, then would this still be a 'population'?" If so, and I then removed another male/female pair, would this be a population too? (etc.).
I was trying to establish at what point the number of male/female pairs ceased to be a 'population' but the discussion either petered out or didn't proceed along those lines, I can't remember which.
Looking back I wonder if not being able to determine (to any meaningful degree) "any change in the frequency of alleles within a gene pool from one generation to the next" might hold the answer.
If so, then the same could be argued for a kaliedoscope: the patterns produced can be analyzed but if I repeatedly removed the coloured pieces of glass producing those patterns then there would come a point where the 'images' produced would be too disjoint for any meaningful information to be gleaned. And there would still be coloured pieces of glass left.
The point, of course, is that only the male/female pairs have a natural reality external to the intellect: you can remove any subset of male/female pairs from a population and perhaps alter the "frequency of alleles within a gene pool from one generation to the next" but you can't do anything to the "frequency of alleles within a gene pool" and affect the male/female pairs.
On another occasion I tried a different tack: If you were to drive by a golf course soon after it started raining then it would come as no surprise to see a few upraised umbrellas among the spectators. If it continued to rain, and you came back ten minutes later, then there might be more umbrellas in evidence.
The question is "Has the population of umbrella-carriers grown or have a number of individuals employed a similar solution to a common set of circumstances?"
From internet discussions it seems clear that some people who are knowledgeable about evolutionary theory can only see that the population has grown.
To even consider the possibility of an internal evolutionary mechanism, on the other hand, requires recognition that a number of individuals found a similar solution - and might share a mutual awareness because of it.
Definiting evolution does not define, limit, or affect how evolutionary changes may or may not occur: go to the furthest ends of the earth and you will only ever see individual organisms, peer through a microscope into the smallest petri dish and you will only ever see individual bacterium. "Herds", "Flocks", "Shoals", and "Colonies" are only descriptive labels - not natural entities!
And you will never, ever, see a "gene pool". Remember Occam's razor:
one should not increase, beyond what is necessary, the number of entities required to explain anythingIf there are only individual organisms in the natural world then wouldn't it be sensible to consider the possibility that evolutionary changes occur because of something inside of them? something testable?
Model of an Internal Evolutionary Mechanism: