“Sharks don’t get cancer.”Many people have heard this, and many people believe it, even if they wouldn’t go so far as to buy a cancer treatment from shark materials. Even the BBC fell for this myth. You can find refutations from Nerdy Christie Wilcox, with some additional info from Why Sharks Matter.
I don’t want to rehash the debunking of the myth here. Instead, I want to talk about why people aren’t rushing out to buy naked mole rats.For animal behaviour researchers, the naked mole rat (Heterocephalus glaber) is yesterday’s news. There was a lot of interest in the social behaviour of naked mole rats in the 1980s when it was discovered that they had some behaviours surprisingly similar to bees and ants.
But it turns out that this species is remarkable in many other ways, not least of which is its apparent immunity to cancer. New Scientist recently had a story about the interesting research being done on naked mole rats.
Nearly all mice have cancerous cells lurking in their bodies by the time they die but cancer has never been seen in a naked mole rat. “Every time one of our animals die, we try to figure out what they die of,” Buffenstein says. “We haven’t seen a tumour, we haven’t seen lesions, we haven’t seen signs of lymphoma. We know they don’t get age-related cancer.”
(“Buffenstein” is Rochelle Buffenstein, who does physiology up the road from us at the University of Texas Health Science Center in San Antonio.)
For that matter, crustacean cancers are also rare (Vogt 2008). (Somewhat ironic, considering that “cancer” can also refer to crabs.) And in discussion with one of my friends whose done real honest to goodness cancer research, I seem to recall her saying that several other groups of mammals rarely got cancer.
Why has the shark myth taken hold of public consciousness when real examples have not?
I think it’s purely magical thinking.
One kind of magical thinking is that things have an “essence”. It might be good or bad, but importantly, that essence can spread. People want to touch an object if they are told it belonged to a famous musician or leader, but will not want to touch it if they are told it belonged to a serial killer.
It’s the same kind of logic that led people to hunt tigers and rhinos for aphrodisiacs. It’s the exact same reasoning that led people to gruesome beliefs like one where you could gain powers using body parts from people with albinism. Or that you would gain your enemy’s strength by eating their heart.
A shark is a powerful. Large. Fearsome.
A naked mole rat is ugly. Small. Comical.
We want to think that sharks can beat cancer. It seems absurd that a naked mole rat could defeat something that causes so much grief in humans. But the real absurdity is how far astray we can be led by magical thinking.
References
Seluanov A, Hine C, Azpurua J, Feigenson M, Bozzella M, Mao Z, Catania K, Gorbunova V. 2009. Hypersensitivity to contact inhibition provides a clue to cancer resistance of naked mole-rat. Proceedings of the National Academy of Sciences 106(46): 19352-19357. DOI: 10.1073/pnas.0905252106
Liang S, Mele J, Wu Y, Buffenstein R, Hornsby P. 2010. Resistance to experimental tumorigenesis in cells of a long-lived mammal, the naked mole-rat (Heterocephalus glaber). Aging Cell 9(4): 626-635. DOI: 10.1111/j.1474-9726.2010.00588.x
Jarvis J. 1981. Eusociality in a mammal: cooperative breeding in naked mole-rat colonies. Science 212(4494): 571-573. DOI: 10.1126/science.7209555
Vogt G. 2008. How to minimize formation and growth of tumours: Potential benefits of decapod crustaceans for cancer research. International Journal of Cancer 123(12): 2727-2734. DOI: 10.1002/ijc.23947
Picture by Smithsonian's National Zoo on Flickr. Used under a Creative Commons license.
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