Josh Swamidass at Washington University is a frequent critic of intelligent design, and we’ve taken issue with him here from time to time. But let’s give credit where credit is due. It requires a certain daring that one can’t help but admire to offer, as proof of unguided evolution’s creative prowess, something as thoroughly counterintuitive as…cancer.
Think of it: the world’s most feared disease and one of its most destructive, presented as knock-down evidence for evolution’s power not to destroy — but to create! Yet this is the argument that Dr. Swamidass, a theistic evolutionist, has advanced over at the BioLogos website.
Cancer make some sense as an objection to intelligent design, if you assume (incorrectly) that ID posits God as the designer and that ID proponents must therefore defend the perfection of all biological design. That’s naïve theology and naïve science, but at least anyone can appreciate the gut-level power of the objection. On the other hand, the cancer-proves-evolution argument seems hopeless at first glance. Building a tumor, a potentially lethal instance of unregulated cell growth, as a parallel to building all the wonderful novelties, features, and functions of animal and plant life? No one is going to buy that.
What about on closer inspection, though? As biologist Jonathan Wells demonstrates in an excellent response published by Salvo Magazine, the Swamidass cancer argument is not much more plausible when you look at it in detail.
What Dr. Swamidass has going for him is primarily a quirk of semantics.
[C]omputational biologist Joshua Swamidass argues that “cancer regularly innovates with proteins of novel function.”2 He calls this “neo-functionalization.” According to Swamidass, this “casts serious doubt on the ID arguments from molecular biology,” namely, that proteins cannot evolve novel functions without the aid of intelligent design. He concludes that if ID were true, “then cancer as we know it would be mathematically impossible, or regularly require the direct intervention of God to initiate and be sustained.”3
That does sound bad for the design argument, doesn’t it? If cancer “regularly innovates,” producing new if malignant functions, via “neo-functionality”? Jonathan Wells concedes, “Many cancers have alterations in their DNA that are called ‘gain-of-function’ mutations.” New functions (echolocation, photosynthesis, the human facility with language) are something that ID folks say unguided evolution can’t explain.
Yet it all falls apart after that, as Dr. Wells goes about his work quickly and dispassionately. As you might suspect, the neo-functions aren’t really functions at all, in the sense of what Darwinian theory struggles to explain. They are functional losses or “perversions” of preexisting function:
Two classes of “genes” (protein-coding regions of DNA) that have been widely studied in cancer are “proto-oncogenes,” which, when mutated, lead to the uncontrolled growth that characterizes cancer cells, and “tumor suppressor genes,” which normally prevent cancer but when mutated fail to block it. The former include genes of the Ras family, while the latter include the TP53 gene.
Ras genes produce signaling proteins that induce cells to divide. In normal cells, Ras proteins (gene names are italicized, while the proteins encoded by them are not) are turned off much of the time, but when mutated, they get stuck in the “on” position (a condition called “constitutive activation”). So they induce cells to divide without stopping.4 Although this is called a “gain-of-function” mutation, the Ras protein hasn’t actually gained a new function. It has simply lost the ability to regulate its old one.5
The TP53 gene encodes a protein called p53 that has many functions. It binds to specific DNA sequences, but it also interacts with many other molecules involved in cell metabolism.6 In normal cells, the functions of p53 prevent the cell from becoming cancerous, but when TP53 mutates, this function is abolished. The mutant protein still binds to DNA, but it has lost its ability to target specific sequences, so it interacts with regions of DNA that are unaffected by normal p53. The mutant protein (designated mutp53) also accumulates at a much higher concentration than normal p53 (designated “wild-type” p53, or wtp53). Like wtp53, mutp53 continues to interact with many other molecules in the cell, but those interactions are now perverted to the point where the cell becomes cancerous and invades other tissues.7
This does not necessarily mean that mutp53 acts through mechanisms different from those of wtp53. The mutant protein binds to more regions of DNA than wtp53, not because it has gained anything, but because it has lost its sequence specificity. And the other effects of mutp53 are not as novel as they seem. According to Israeli cancer researchers Moshe Oren and Varda Rotter, “given the high concentration of mutp53 protein in tumor cells, relatively weak molecular interactions, which are marginal within the wtp53 protein, may now be amplified by mass action and reach a threshold that allows them to exert a measurable impact on biochemical processes within the cell.”8
In 2012, philosopher of biology Pierre-Luc Germain emphasized that the “new” functions in cancer cells “are not complex adaptations; in other words, they are not the result of cumulative evolution. . . . Instead, it is the pre-existing wiring of the cell which best accounts for these features.” In other words, “healthy cells — their structure, possible states, pathways, and weak spots — already contain the resources to be drawn upon and developed by cancer cells.”9
So the neo-functionalization that Swamidass attributes to cancer cells is really the de-regulation and perversion of existing functions, rather than the creation of new ones.
As Dr. Wells concludes, originating species and originating tumors are really “polar opposites” and you can’t learn anything about the former from the latter. This really should settle the question, and I would encourage Dr. Swamidass and other writers and commenters at BioLogos to read and think about Dr. Wells’s dismantling of his case.
Is cancer, then, the latest “icon of evolution,” that stands to be embraced by Darwin proponents as a rhetorical mascot for their argument, only to be knocked down by Jonathan Wells? See his books Icons of Evolution and Zombie Science. Wells does deal with the cancer argument, as innovated by Joshua Swamidass, in Zombie Science.
The problem is that unlike with other icons (such as whale evolution, Darwin’s finches, or peppered moths), the feature of surface plausibility is, as I mentioned earlier, so conspicuously missing here. That is going to hamper this would-be icon from finding its way into the textbooks.
Photo credit: National Institutes of Health (NIH) (National Institutes of Health (NIH)) [Public domain], via Wikimedia Commons.