Dr. Michael Egnor, creationist neurosurgeon and Discovery Institute blogger, has a problem. Either he hasn’t figured out that we’re way past April Fools Day, or he has just managed to produce what might just be the single dumbest anti-evolution argument that I have ever seen. We’re talking about a demonstration of absolute, rock-bottom, Kent-Hovind-eat-your-heart-out, triple-distilled essence of pure stupid.
The argument today – and I warn anyone who knows anything at all about evolution to put down all food and drinks right now – is that if evolution was right, we should see some brain tumors acting to make better brains.
No, I’m not joking. That’s his latest argument, in response to a thorough fisking delivered last month by Yale neuroscientist Steve Novella. Brain tumors mutate and are subject to natural selection, so if evolution is correct they should produce better brains:
Dr. Novella is missing a much better example of random mutation and natural selection that’s not metaphorical at all. Cancer is a test of Darwin’s theory. Cancer is real biological evolution by random mutation and natural selection, writ fast. There’s no reason to invoke encyclopedia typos or tractor engines in order to understand what “chance and necessity” can do to a living system. Brain tumors are perfect little Novellian “two-cycle engines” nestled inside the skull, “random mutations” coming out the ears, and “natural selection” like there’s no tomorrow (excuse the metaphors). Brain tumors are constantly generating new biological variation, and they are avatars of natural selection. They provide a tremendous spectrum of variation, from “variation jet-engines” like malignant glioblastoma multiforme to “variation tortoises” like benign pilocytic astrocytomas. Cancer wards are full of patients brimming with “two-stroke engines” of evolutionary change.
Not content to stop with a single bloody stupid argument, Dr. Egnor grabs his trusty shovel and keeps digging his hole:
The best real biological test of “shuffling around information, duplicating, and altering the information” is cancer. According to Dr. Novella’s reasoning, brain tumors ought to be generating quite a bit of “meaningful and even useful new information.” Better neuroanatomy and better neurophysiology ought to be popping up “easily.” Better frontal lobes and cognition, from cancer. Better temporal lobes and memory, from cancer. Better cerebellums and coordination, from cancer. If random mutations and natural selection–Dr. Novella’s “two stroke engine”–is the source of all functional integrated biological complexity, brain tumors ought to help our brains evolve in some way.
Perhaps Dr. Novella has data that show real evolutionary improvements in the brain caused by brain tumors. If he has, he should show us.
I’m just a rube, not a Darwinist from Yale. But I’ve never seen cancer make a brain better.
Excuse me for a second while I reboot my frozen-in-disbelief brain. OK. That’s better.
Let’s start with the remedial explanation of “natural selection.” Natural selection acts on heritable variation. That’s variation that can be passed on to subsequent generations. Any heritable variation that increases the survival in subsequent generations is selected for, and becomes more common in the population. Any variation which does not get passed down to subsequent generations cannot be acted on by natural selection. That’s a really, really, really basic concept in evolution.
The mutations within the tumors – the variation that Dr. Egnor is talking about – take place within cancerous cells in the brain. These mutations do not take place in egg or sperm cells. If the mutations don’t occur in eggs or sperm, they are not heritable within the human population, and are not subject to natural selection at that level.
The mutations within the tumors are heritable in a very, very limited sense – they can be passed on to subsequent generations of the tumor cells. Mutations which result in a tumor cell making more tumor cells do get passed on, and you get more tumor cells as a result. Mutations which don’t result in a tumor cell making more tumor cells aren’t selected for, and don’t get passed on as well.
Oh, and by the way, we do know that sometimes mutations within tumor cells do make those tumor cells start to produce more tumor cells, which then produce in turn more tumor cells, and so on. When that happens, the cancer gets worse for the person who is hosting the cancer. From the perspective of the cancer, things are getting a lot better – right up to the moment when it kills its host.