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August 25, 2015

Pediatric Cancers: Their Evolutionary Significance


The idea that selected changes in Bilaterian's bodies would cause an increase in juvenile cancer rates has been part of my theory from its inception; it was clearly expressed in the 1984 Journal of Theoretical Biology Letter as it was in manuscripts submitted to other journals as early as 1979.   

Here is a relevant paragraph from the 1984 Letter: 


Adaptive pro-oncogenes are those that imparted some survival benefit to the germ line in spite of a likely increase in juvenile deaths from cancer fol­lowing their selection.  Increased somatic complexi­ty, greater body size, ex­tended pre-reproductive life and migration to more mutagenic habitats occurred in so many Bilaterian lineages that they can be confi­dently judged to have been adaptive.  It is, however, most probable that selection of such characters was followed by increases in the incidence of somatic mutational events in juve­niles and resulted in in­creased losses of genetic material to cancer.

How did I reach that conclusion? Well, there is a limited number of tools one can use in theorizing about events that occurred in the deep past and one of them is "probabilistic" reasoning. Based on common sense and the "learning curve" experience of modern manufacturers, I thought it likely that gene pools that were constructing animals with parts that had been recently modified were likelier to commit errors in replicating those parts than they were to commit similar errors in parts that had not been recently modified.

Here is an overview of relevant pediatric cancers that seem to support this part of my theory.

Brain cancer. We know that the human brain reached its current form relatively recently, about two million years ago, compared to the origin of Bilaterians (and, according to my theory, cancer) about 550 million years ago.

Leukemia/Lymphoma. Our immune defenses must adapt
—changecontinuously to cope with evolutionary modifications in pathogens.

Bone cancers originating in arms and legs. Human limbs are longer than those of other primates, strongly suggesting that they are longer than those of our direct pre-human ancestors. These cancers occur in adolescents as well as in younger children.

Retinoblastoma
.
The human eye, perhaps our most finely wrought organ, probably underwent  perfectionizing modifications throughout evolutionary time, including the relatively recent. This rare eye cancer occurs most frequently in young children.


At present, the most common sites-of-origin cancers in American children are leukemia/lymphoma and brain cancer. 

I describe the critical evolutionary role played by cancers in modified tissue throughout Bilaterian evolution in Chapter Three of my book Cancer Selection. In my opinion, the present-day occurrence of pediatric cancers confirms the continue presence of the powerful selection pressure that compelled nothing less than utmost perfection in the expression of modifications in the development program. Some indirect acknowledgement of this evolutionary dynamic was expressed by Crespi and Summers when they wrote, with my book cited as their source, that following the selection of certain morphological changes " ... increased cancer rates evolve as a more or less transitory evolutionary byproduct."


Comments and questions are welcomed here.

At this site you will find links to additional material including my original Letters to the Journal of Theoretical Biology and  the 1992 Nature review of my book.

Copyright © 2015 by James Graham

This page was archived at Way Back Machine on August 25, 2015.
Comments and questions are welcomed here.

At this site you will find links to additional material including my original Letters to the Journal of Theoretical Biology and  the 1992 Nature review of my book.

Copyright © 2015 by James Graham

This page was archived at Way Back Machine on June 29, 2015.

- See more at: http://cancerselection.blogspot.com/2015/06/updated-visitors-to-this-site-and-their.html#sthash.OU3IBbTU.dpuf
Comments and questions are welcomed here.

At this site you will find links to additional material including my original Letters to the Journal of Theoretical Biology and  the 1992 Nature review of my book.

Copyright © 2015 by James Graham

This page was archived at Way Back Machine on June 29, 2015.

- See more at: http://cancerselection.blogspot.com/2015/06/updated-visitors-to-this-site-and-their.html#sthash.OU3IBbTU.dpuf
Comments and questions are welcomed here.

At this site you will find links to additional material including my original Letters to the Journal of Theoretical Biology and  the 1992 Nature review of my book.

Copyright © 2015 by James Graham

This page was archived at Way Back Machine on June 29, 2015.

- See more at: http://cancerselection.blogspot.com/2015/06/updated-visitors-to-this-site-and-their.html#sthash.OU3IBbTU.dpuf