A Prohibited Animal

According to Karl R. Popper, in comparing two competing theories, the one that forbids more occurrences in the natural world—that lists more possible refutations—is superior to one that forbids fewer. (1)

In Chapter Thirteen of Cancer Selection I describe three separate and distinct refutations of my proposed fundamental amendment to the neo-Darwinian theory of evolution. In one refutation I describe an imaginary animal, one that possesses a constellation of particular characteristics, each one of which can be found in abundance in Nature, and assert that such an animal cannot exist; find one forbidden specimen and my theory is refuted.

Who Has Been Visiting This Site?

Now that the site has accumulated a few thousand page-views, it might be interesting to view a summary of visitors' geographic location.

    USA                               57.4%
    Russia                           10.8
    Germany                      10.6
    France                             4.8
    United Kingdom             4.0
    Ukraine                           4.0
    China                              4.0
    All Other                         4.4 
    
    Total                           100.0%

On the Origin of Bilateral Symmetry

It is a fundamental principle of evolutionary theory that Nature never anticipates. A gene pool cannot plan for changes in the environment, for the possible future emergence of new predators or any other contingency; the existential threats any gene pool ever encountered existed in the here-and-now. In this posting I propose that bilateral symmetry was originally selected, not for its future mobility-enhancing potential, but because it functioned as a cancer-preventing device in the earliest Bilaterians. 

Those familiar with my published theory know it asserts that all multicells can be divided into two mega-groups: those constructed of somatic cells which all contained functioning cancer triggers (oncogenes) and those that were incapable of dying of cancer. As my peer-reviewed 1984 Letter in the Journal of Theoretical Biology stated succinctly, "This theory states that oncogenes, thus defined, have been present in every cell of every specimen of every species of the Bilateria that ever existed, and that they have existed nowhere else in Nature."

My 1983 Letter asserted that evolutionarily significant lethal cancer did occur in developing Bilaterians in numbers sufficient to create selection pressure for the accumulation of anti-cancer mechanisms and, because cancer begins with replication error, that all those defenses " ... enhanced the ability of the genomes to create organisms in which the genetic program is expressed with great fidelity in all somatic cells." (1)
 

I am convinced that one of the earliest anti-cancer adaptations was rejection of the radial symmetry found in other multicells (including the likely ancestors of Bilaterians) and selection of symmetry along a longitudinal axis, a radical departure that enabled gene pools to produce sufficient numbers of animals free of cancer during development.

Cancer Discovered in Hydra?

It has recently been reported here and here that scientists at Kiel University in Germany claim that cancer has been found in Hydra.

Anyone familiar with my published theory knows it asserts that lethal juvenile cancer occurred in all Bilaterians and only in Bilaterians, that other multicells including cnidarians like Hydra did not experience it during evolution.

So does this report from Kiel University conflict with my theory? 

On Peto's Paradox

"Peto's Paradox is the observation ... that at the species level, the incidence of cancer does not appear to correlate with the number of cells in an organism."

Do blue whales seldom get cancer?

Being a cautious fellow I don’t know whether or not it is true that blue whales get less cancer than (say) mice but I do accept that fewer cases of cancer have been reported in blue whales than in smaller vertebrates. Caution also tells me that neither I (nor anyone else) has, at present, access to technology that enables one to observe an animal’s somatic cells as they are transformed to the cancerous state. Nor can we observe whether such cells are promptly extinguished by agents of an adaptive immune system (which all vertebrates possess) before producing cancerous daughter cells in sufficient numbers. Sufficient, that is, to cause death from cancer or to produce detectable symptoms. 
  

So, my starting point is different from others who have written extensively on this subject. My view is that—most probably—blue whales, because they consist of greater numbers of somatic cells, produce a greater number of cells transformed to the cancerous state than do mice but, as I will explain below, their greater size enables them to minimize production of detectable cancer.