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October 27, 2015

Cephalopod Secrets


In the years prior to achieving publication of my theory I sent copies of my latest draft to individual scientists in the hope that they might offer encouragement or useful criticism. Mostly I contacted evolutionary biologists, but occasionally I sent the draft to cancer researchers.

In 1978 or 1979 a well-known cancer scientist responded to my latest version by cautioning me about my assertion that the immune system of vertebrates was capable of killing cancer cells; he said it wasn't clear that immune systems could do that. 



Despite his advice I was confident that my reasoning was sound; vertebrates could not have flourished on land without a highly-efficient means of killing cells already transformed to the malignant state. That conviction was eventually published in my 1983 Letter where I pointed out that because such an immune system was an efficient "fail-safe"device it enabled the "retirement" of defenses that prevent the initiation of cancer.
"The evolution of efficient cancer-specific immunological defenses in all vertebrates would have enabled those species to adapt characters, functions, etc., which might have increased the incidence of cancer initiation. The following all suggest the lowering of first line defenses against cancer in vertebrates: increased mitosis as evidenced by large body size and extended pre-reproductive life, increased exposure to radiation as the result of migration from aquatic to terrestrial habitats, and the elimination, in many mammalian species, of opaque external protection from UV radiation.(1)


Although I also wrote in Chapter Nine  of Cancer Selection about the "lowering of first line defenses against cancer" in terrestrial vertebrates whose ancestors had left the less carcinogenic marine environment to inhabit land areas, I believe the same phenomenon occurred among the cephalopods. Although likely descended from mollusks whose soft parts were shielded from environmental radiation behind thick shells, certain cephalopodsoctopus, squid and cuttlefishsurvive without that protection. I believe these mollusks were able to dispense with external opaque covering because they had acquired other powerful defenses against lethal cancer.

Investigators are discovering previously unknown cancer defenses in other Bilaterian species. In 2013 researchers found that naked mole rats produce the substance hayaluronan which seems to explain why those rodents don't get cancer.
More recently, researchers found that African elephantswhich have low cancer ratespossess multiple copies of gene TP53. Perhaps investigations will reveal why some mollusks can flourish without the anti-cancer protection afforded by thick external shells.

Anyone who has read this posting on echinoderms will recognize that I am using similar logic. My theory says most Bilaterians do not regenerate damaged body parts as efficiently as other multicells because to do so would risk cancer initiation. Because starfish appear to ignore that risk
they even regenerate amputated complex organsI inferred that they might possess undiscovered cancer defenses. My theory also says that the near-universal presence of external opaque covering in invertebrate Bilaterians implies that the coverings act as cancer deterrents (2); therefore, any invertebrates that survive without shielding probably acquired other powerful cancer defenses. (3) (4)  
 

NOTES

(1) I am now convinced that larger body sizes actually added to the efficacy of immune systems; when encountering young populations of malignant cells animals with larger bodies can muster greater numbers of cancer-killing entities, e.g., T-cells.

(2) I need to make clear that I know external coverings serve other functions, such as defending against predation. A scientist who had read my book told a journalist that I thought snails' shells had a single function: to protect against cancer. This individual apparently needs to portray himself as my intellectual superior; he claims that I, a person with no scientific training, managed to be published twice in a Biology journal but remain both ignorant and stupid. (I don't even mention snails in the book.) Unfortunately, the journalist published his asinine comment. 


(3) In my 1984 Letter I wrote "Those [Bilaterian] germ lines that created the most complex animals endured the most genetic losses to cancer and vice versa." In other words, my theory says that the most complex animals (including, of course, humans) are products of extraordinary selection pressure to accumulate and to perfect defenses against lethal cancer, especially in juveniles. As even a casual reading of the literature will confirm, the octopus is one of the most complex invertebrates, making it more likely to possess a broader array of effective defenses against cancer than its less complex relatives such as clams, oysters and other bivalves. 
 

(4) If future investigators were to confirm that giant squid experience, as I would expect, little or no cancer some people might mistakenly proclaim that to be a "paradox," that large animals ought to experience more cancer than the small. As I've written elsewhere there is no paradox, simply a failure to accept that all Bilaterians were produced by lineages that had been subjected to intense selection pressure to accumulate cancer defenses.


Comments and question 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 October 27, 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