A FACT-BASED EXERCISE
PART TWO: A PROPOSED SOLUTION
Although in Part One I used the legitimate analytical device of limiting to actual breeders my introductory examination of the historical evolution of Bilaterians, in reality throughout their long history of ~550 million years all Bilaterian gene pools were producing complete populations of animals, including those juveniles that did not survive development. And to understand how the actual breeders could have produced those unbroken chains of perfection we need to consider what mechanisms, operating on entire populations, could have favored that outcome. Before doing that I need to explain why I find certain terms favored by many biologists less than useful in this exercise.
I consider “negative selection” and “positive selection” unnecessary and misleading in considering, as I am, evolution over deep time. Yes, there were “victims” of selection (animals that died as juveniles) and “beneficiaries” of selection (the breeders) but they were all products of the same force: natural selection operating on the entire population. Juveniles afflicted with mal-formed vital organs died from those specific mal-developments and juveniles with perfectly formed organs (barring, of course, other causes of early death) passed their “genes for perfection” to offspring.
Some refer to the elimination of mal-formed juveniles as “stabilizing” selection. Again, I consider attempts to narrow the definition of selection by such gratuitous parsing not only unhelpful but profoundly misleading. If one thinks that lethal juvenile cancer was only an instrument of “stabilizing” selection because it eliminated imperfectly formed developing animals, it misses entirely the role played by selection pressure resulting from such deaths, pressure that enabled the affected gene pools to produce with great precision the most complex things known to exist in the universe.
THE EERIE EFFICIENCY OF SELECTION
As I wrote in my August 27th posting I was perplexed by the reaction of two scientists to my idea; they said I was probably correct but I was wrong to insist that my idea was a radical departure from Neo-Darwinism. Here’s where I think they may have erred: they applied short-term thinking to the problem I address which is the entire history of Bilaterian evolution. They were probably thinking that cancer-caused deaths of individual juveniles was just another form of “stabilizing selection” and that I was therefore wrong to insist that without those deaths Bilaterians would not exist.