Cancer and Evolutionary Theory

[Swamidass (Peaceful Science)]

Good questions Jon! Thanks for the note…

@Jon_Garvey

But I’m still having some trouble getting my head round the concept of “tumours evolving” rather than “populations of organisms evolving new susceptibilities to damage.” It sounds to me to be a metaphorical use of “evolution” that potentially functions to redefine mutations “deleterious to organisms” (the commonest type, because breaking stuff is easy) as “beneficial to tumours”.

I see your objection and am sympathetic because I held it for a long time too. It is easy to dismiss all we have learned about cancer and its relation to evolution as an example of things “breaking down,” but look at this from the point of view of cancer cells “evolving” is perhaps the dominant paradigm, and is a more accurate approach for a few reasons.

1. Cancer cells are not “less” functional, as if they were broken. In fact malignancy requires several (some estimate up to 15) often convergent genetic changes (i.e. angiogenesis, cell-adhesion, etc.). The preferred term is “disfunction” because it recognizes correctly that cancers are functioning inproperly (not failing to function), and this is often achieved with neofunctionalization,at a molecular level, something that many ID people think is impossible. This fits the evolution paradigm better the broken paradigm.

2. Cancer cells clealry adapt to their environment and this is fundamentally important to treatment, because they develop resistance to drugs by evolutionary processes.

3. As a model system for evolution, it is particularly useful because the genetics of cancer match humans better than any other model. There are whole classes of mutational systems (e.g. splicing variants) that can cause cancer but are not really at play in microbial systems.

4. All the mathematical machinery of population genetics and neutral theory seem to work exactly as we expect they would on cancer. So perhaps it is an analogy (because cancer is not an independent organism). Though, some versions of cancer do function like transmissible parasites (Canine transmissible venereal tumor - Wikipedia) but that is atypical.

5. Finally, the reasoning we use is identical to evolutionary reasoning. We use data in the present to make inferrential statements about the past.

Now, you are are right, cancer is not exactly evolution, because new species are not evolving. That is where the analogy breaks down. I, rather, think of each tumor as its own independent evolution experiment (and also a tragedy for the patient that we want to cure).

@Jon_Garvey

…or regularly require the direct intervention of God to initiate and be sustained. I’m not sure which option is harder to believe.

That seems to be a theological, not a scientific, statement. It always plays well to deny the involvement of God in anything harmful (though of course in the Bible God does actively send tumours, albeit bubonic rather than malignant ones), but the question needs to be argued, not assumed. If it is hard to believe in principle that God (or why not the devil, if one is a believer in fallen creation?) would be associated with these genetic changes, then one is saying that they are excluded from God’s providence.

I think you are missing what I meaning. What I am saying is different.

If many ID arguments about neofunctionalization and molecular convergence being impossible are true (as many ID proponents are convinced), how do we explain neofunctionalization and molecular convergence in cancer? Clearly it is the same biological system, and we are seeing neofunctionalization and molecular convergence, and all the same genetic patterns in cancer tumors that we see in, for example, humans the the great apes.

In the case of evolution, we look at this data and some ID proponents conclude that it must have required God’s (thought they would say “designer”) direct intervention somehow (from tinkering to special creation).

In the case of cancer, the data looks very very similar. If the ID proponents are right aboutevolution, why would we conclude anything different here?

To take the theology out of it, i should have said,

or regularly require the direct intervention of [an intelligent designer] to initiate and be sustained. I’m not sure which option is harder to believe.

The point is not about theology (though it certainly raises theological questions) but is a question of how the ID scientific logic is applied in two places (evolution and cancer) where we have nearly identical genetic data.