If you think the astonishing complexity and functionality and internal balance of living things is sure evidence for our design -- if you think living bodies are intricately- tuned machines that simply had to have been put together by a conscious hand -- then how do you account for the parts of the machine that are just... well, goofy?
I've just finished this book, Kluge: The Haphazard Construction of the Human Mind. Written by psychology professor Gary Marcus, this "evolutionary neuropsychology for the layperson" book explores how the human brain and mind evolved -- not by looking at how the mind works, but by looking at how it doesn't; by looking not at its astonishing achievements, but at its laughable failures. And along with being a fascinating and funny look at how the human mind works (always one of my favorite topics), it offers one of the best arguments for evolution -- and against any sort of belief in intelligent design, or indeed any sort of interventionist god that tinkers with evolution -- that I've read in a while.
The main point of the book: The human brain is a kluge.
And it's a kluge because evolution is a kluge.
Pronounced "kloodge" (it rhymes with "stooge"), a kluge is an engineering term for an ad hoc solution that's inelegant and imperfect but basically functional. It's a solution that's required because you can't start over from scratch: you have to work with an existing design. You need more space in your house, say, and you don't want to tear the whole house down and start over -- so you stick on an extra room at the side. It's clumsy, it looks funny, it doesn't have good access to the bathroom... but it's cheaper and less disruptive than tearing down the house and building a whole new one with an extra room. And it's fine. It'll do.
Evolution is a kluge. It's the klugiest kluge that ever kluged.
The process of evolution happens gradually, with small changes being made on a previous arrangement. So it can't wipe the slate clean and start again. It's way more constrained even than an engineer. An engineer can say, "You know, it'll be more expensive, but if you tear out these cabinets and move your stove to the other side of the kitchen, you'd have a much better setup. The basic shape of your kitchen is still gonna be weird... but it'll be a lot better than if you leave the layout as is." Evolution can only take the cabinets out one shelf at a time; it can only move the stove an inch at a time... and it can only do it if each step of the process, each removed shelf, each inch that the stove moves across the floor, confers a selective advantage over the previous step. (Or at least, doesn't confer a disadvantage.) There are arguments among evolutionary biologists about exactly how big those steps can be (can the stove move one inch at a time or four inches at a time?)... but the basic principle is the same. Each generation is a modification of the previous one.
So if evolutionary forces are pressuring a four-footed species to stand upright, for instance, it'll have to happen by gradual alterations to the all-fours setup. And if that means bad backs and bad knees and bad feet... tough beans, pal. (I am somewhat bitter on this point, having just turned 47.) Evolution is both callous and lazy: if you survive long enough to reproduce with fertile offspring who can also survive long enough to reproduce, then evolution doesn't give a shit about anything else. There's no evidence of any guiding hand coming in and fixing things so they work a little better. In fact, there's plenty of evidence to suggest otherwise.
And this isn't just true of our knees and our backs and our feet. It isn't just true of our eyes, wired backwards and upside-down; and our vagus nerve, wandering all over hell and gone before it gets where it's going; and our vas deferens (well, not mine, but you know what I mean), ditto.
It's true of our brains, and our minds.
You have to read the book to get the full details. I'm not going to recount the whole thing here. But our memory, our language, our decision- making processes, our mental health, the way we pursue happiness and pleasure, the way we decide what to believe and what not to believe... none of these work optimally. We can remember a face from a 30- year- old yearbook, but we can't remember what we had for breakfast yesterday. We make choices based on shoddy cost- benefit analysis, poor understanding of probability, and immediate satisfaction over long- term gain. Our languages are beautiful and expressive... but they are also imprecise and confusing, often wildly so, and sometimes with serious consequences. Our pursuits of pleasure and happiness are often not just counter- productive in the long run... they often don't even give us much pleasure or happiness in the short run. Our mental health is fragile and easily disrupted.
And don't even get me started on belief.
These systems work pretty darned well, all things considered. We wouldn't be such a thumping evolutionary success if they didn't. But all of them show clear signs of having been kluged onto previously existing mental systems. We are living in a complicated, highly technical, deeply interconnected civilization... with minds that evolved on the African savannah, to find food and shelter, and have sex, and escape from predators, and generally survive just long enough to produce the next generation. Our minds evolved to escape from tigers, not to prevent global warming. And the minds on the African savannah evolved from previous forms, which also evolved from previous forms. The human mind was kluged onto the mind of its monkey ancestors, which was kluged onto the mind of its tetrapod ancestors, which was kluged onto the mind of its fish ancestors, and so on, and so on, and so on.
Which brings me back to intelligent design. And indeed to theistic evolution: the idea that evolution proceeded the way scientists describe it, but that this process was and is guided by the hand of God.
The klugey, ad-hoc, cobbled- together, Rube Goldberg nature of so many biological systems -- including the systems of the human mind -- throws the whole idea of any sort of all- powerful, all- knowing, interventionist god into a cocked hat.
If we really were designed by a perfect God, why would our bodies and minds be so klugey? If God is so magic that he can invisibly tinker with our DNA and make our legs just a skosh longer than our parent's generation -- or our minds just a skosh better at risk-benefit analysis -- then why isn't he magic enough to do a full-scale overhaul? Why wouldn't God reach into the fetuses of the next generation and go, "You know, this generation isn't having so much trouble with immediate survival, and at this point they really need better long-range planning abilities instead. Let's just reach in there, and turn the volume way down on the short-sightedness. And while I'm at it, this vagus nerve is bugging me. I know it had to look like that for the fish, but... okay, there we go. Much better. And let's seriously re-think those knees. For a quadruped, sure... but for a biped? What was I thinking? Makeover time!"
There is no evidence that this has ever happened. Even to the smallest degree.
There is, instead, ample evidence to the contrary. There is ample evidence for the idea that evolution is an entirely natural process: descent with modification, from one generation to the next, with each generation being a modification of the one before it.
And the klugey, Rube Goldberg, "work with what you've got" nature of our bodies -- including the part of our bodies that produces our minds -- is Exhibit A.