How Did Bilaterian Evolution Happen? (Continued)

A FACT-BASED EXERCISE

PART TWO: A PROPOSED SOLUTION

POPULATIONAL THINKING

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 27^th 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.

How Did Bilaterian Evolution Happen?

A FACT-BASED EXERCISE

PART ONE: THE PROBLEM REDEFINED

My objective in this two part posting is to consider the fact of Bilaterian evolution in a new way, one that, in my opinion, both reveals the inadequacy of conventional theory and identifies its replacement.  Reading both parts will consume only a few minutes, but it is my hope that they will inspire others to give the problems I describe sufficient thought.

Although it may seem counter-intuitive, those of us who resolutely view evolutionary biology as an historical science have certain advantages over those who primarily employ tools of observational science. We cannot observe past events and we certainly cannot climb into a time machine and perform experiments in the pre-Cambrian, but because we accept Bilaterian evolution as fact we can reach certain useful conclusions, conclusions that demonstrate the gross inadequacy of conventional theory.

To begin this exercise, the most useful conclusion to be drawn from the fact of evolution is that not a single ancestor of any animal that ever existed died as a juvenile. It is a tautological certainty: because only adults breed we know that all the actual breeders survived pre-adult life. From that indisputable fact we can infer, with utmost confidence, that every breeder was the beneficiary of “perfect” development. (Convinced as I am that reproduction by significantly mal-developed animals was extremely rare in the past—as rare as it is in the present—I place “perfect” in quotes simply to deflect potential nitpicking.)

The fact of evolution permits me to state—also with certitude—that these links of perfect development—perfect animals begetting perfect animals—in all the chains that produced all extant Bilateria never once broke: all extant animals are products of uninterrupted chains of perfection.

THERE IS NO MODEL …

In a friendly email exchange I had not long ago with a research scientist who had read my book he asked if I had a model to support my theory. If he asked that question today I would say that he could find a suitable “model” in many biology textbooks; it’s the standard “tree of life” showing biologists’ best estimate of the various Bilaterian lineages’ relationship to one another and to the founding Ur-Bilaterians.  Included in this exercise are all chains of perfect construction of actual ancestors of all living animals in all extant species of Bilaterians: millions of lineages producing millions of trillions of breeders over ~550 million years.  

BUT THERE IS A CONTROL GROUP ...

According to my theory only the Bilaterians are products of cancer selection; except in cases like flowering plants which co-evolved with certain Bilaterians, I agree with the consensus that the evolution of all other multicells is adequately explained by Neo-Darwinism’s mechanism; cancer selection played no part in their history. 

As my control, to compare with the unbroken chains of breeding Bilaterians, I nominate the jellyfish. According to this report fossil evidence shows that more than 500 million years ago jellyfish “showed the same complexity as modern jellyfish.” In other words, in their lineages the unbroken chains of perfection might be summarized as “perfect jellyfish begetting perfect jellyfish without easily discernible morphological changes” for more than 500 million years.