Luck organs

Adam Felber at Fanatical Apathy just wrote a post suggesting that if "Intelligent Design" is a serious argument, then one must recognize that the "design" of human beings - with their fragile knees and spines and appendices, big heads and small birth canals - falls a little short of most definitions of "intelligent".

I've written in the past about what I call "biological practical jokes", situations in human physiology that are so perversely ironic that they could be held as evidence of malicious intent on the part of any purported "designer." (I do not believe in a "malicious designer", by the way.)

There is another aspect of human life that I have always wondered about. We humans are prone to defects and aberrations: bad eyesight, bad teeth, poor ability to regulate blood sugar, etc. In the dim dark ancient days of, say, three hundred years or more ago, I cannot imagine that many people with crappy eyesight, a mouthful of rotting teeeth, or lying on the ground in a diabetic coma had much opportunity to reproduce. Not that some of them didn't manage to get laid, but I imagine people with good eyes and decent teeth and an ability to eat whatever whenever without worrying about dying probably did a lot better in that arena.

But then we humans compensated for our frailties with technology. Bad eyesight? Here's some glasses / contact lenses / radial keratonomy / laser surgery to correct your vision. Bad teeth? Go to the doctor to have them pulled / filled / resurfaced / straightened / replaced - and here's some toothpaste and dental floss and instructions on how to use them. Can't control blood sugar? Here's some insulin and a list of dietary recommendations, and maybe some medication to keep you in balance.

So we go around with our defects compensated for (but not corrected or eliminated) by technology, and we go on happily copulating and squeezing out little ones who carry our genes. And that's all well and good, as long as the plug doesn't get pulled on technology.

But there are some other things in human physiology that make you scratch your head. In a pre-technological (or at least pre-surgical) society damage to them would have almost certainly resulted in death. Things like the appendix, whose proper biological function is uncertain and possibly nonexistent, but whose malfunction can result in death; or the spleen, which does perform a known biological function but is not absolutely necessary to life, yet is so susceptible to damage through injury or disease that it is frequently removed as a result because its malfunction is a threat to life.

So why do we have an appendix or a spleen? Let's ignore (or dismiss) any arguments about the "mysterious ways" of an intelligent designer and look at it purely from an evolutionary point of view. Why do we humans still cart around genes for these fragile, dangerous things that we could probably just as easily do without?

I propose that these organs are a biological indicator of difficult-to-measure factor: luck.

Granted, there's a lot of luck involved in evolution overall. Only organisms that are strong enough, or clever enough, or sneaky enough, or persistent enough, or lucky enough get to pass on their genes to the next generation. If you were the sort of kid who tended to wander into the middle of busy street, odds are you never made it to adolescence with a fully functioning reproductive system. Or maybe you did, but you got banged up a little. Maybe a lot. And maybe you had to make a trip or two to the hospital for a little life-saving emergency surgery.

Once upon a time there wouldn't have been that sort of emergency surgery available for pre-adolescents who got gored by a Woolly Rhinoceros or an Irish Deer and had their appendices or spleens ruptured. They would have died, slowly and painfully, and their genes would have died with them. Meanwhile their companions, who were quick enough or clever enough or lucky enough to avoid getting gored in the first place, would have gotten the opportunity to grow to sexual maturity and pass on their genes to a new generation - including the genes for their spleens and appendices.

It's not a strong argument for why we carry around vestigial or semi-vestigial organs that amount to little packets of unstable explosives stored here and there in our bodies. It doesn't explain why those individuals born without an appendix or a spleen don't have a strong reproductive advantage over those of us born with all our organs intact. Still, it is an interesting avenue of thought to explore: the possibility that the presence of organs that are non-essential in their function, fragile and easily damaged, and lethal in their damaged state may actually be an aspect of natural selection for a characteristic as intangible as "luck."