Cutting Through The Crap

Friday, January 15, 2010

Balanced






Saw this on Pharyngula. I like it.

4 comments:

Anonymous said...

Not arguiing for either side here, but I wonder about a few things in nature.

How would evolution create the Bombardier Beetle? That little sucker mixes Hydrogen Peroxide with Hydroquinone and enzymes in it's belly, let's the pressure build, and then fires the boiling stuff at adversaries. How the heck could that bug combine those substances AND develop the internal organs to protect itself from being burned when those substances mix AND learn to fire it accurately? Did it first naturally select for a 2 chambered mixing system, and then select for the toxic substances later?

How about how the sympathetic tracts in the midbrain run through the Periaqueductal Gray, allowing an animal being eaten by a predator to benefit from a rush of opioids in it's last moments. I'm not sure how natural selection would select for something that is relatively pain free while it's being eaten, since the animal with that beneficial trait is becoming a snack rather than procreating. My best guess would be that that opioid burst would also help the animal escape danger despite being hurt or in pain, thus allowing it's natural selection in the gene pool. It still makes you think....

Regards,
PrecordialThump

Sid Schwab said...

PT, I'd thought about the opioid thing, too, and had come to the same conclusion.

For the beetle, you're making the "irreducible complexity" argument, which has been explained repeatedly, in terms of the classic creationist "eye" argument, the tornado in the junkyard, clotting pathways, etc. Nor are we more than barely able to fathom the meaning of a few billion years, let alone a million, in terms of evolution.

To me, it's far harder to imagine something as complex as a creator-deity existing without creation. Was it by an even more complex creator deity, regressing infinitely?

Sam Spade said...

PrecordialThump: Consider that man turned the wolf into the dachshund in a few thousand years, and that life has been on this planet for about 2 billion years. Now, tell me how much money you'd have if you invested $100 at 7% interest for 1,000,000 years.

My point is that humans can't intuit even a simple exponential function. Why do you expect the effects of 2 billion years of one of the most complex systems we know of to be intuitive?

Here is a specific, though theoretical, answer to your question:

One plausible sequence (much abbreviated) is thus:

1. Insects produce quinones for tanning their cuticle. Quinones make them distasteful, so the insects evolve to produce more of them and to produce other defensive chemicals, including hydroquinones.
2. The insects evolve depressions for storing quinones and muscles for ejecting them onto their surface when threatened with being eaten. The depression becomes a reservoir with secretory glands supplying hydroquinones into it. This configuration exists in many beetles, including close relatives of bombardier beetles (Forsyth 1970).
3. Hydrogen peroxide becomes mixed with the hydroquinones. Catalases and peroxidases appear along the output passage of the reservoir, ensuring that more quinones appear in the exuded product.
4. More catalases and peroxidases are produced, generating oxygen and producing a foamy discharge, as in the bombardier beetle Metrius contractus (Eisner et al. 2000).
5. As the output passage becomes a hardened reaction chamber, still more catalases and peroxidases are produced, gradually becoming today's bombardier beetles.


All of the steps are small or can be easily broken down into smaller ones, and all are probably selectively advantageous. Several of the intermediate stages are known to be viable by the fact that they exist in other living species.

Anonymous said...

Sam,
Thanks for the article re: bombardier beetles. Sometimes I wish evolution gave me some cool toys like that. Instead, all I got are these opposable thumbs.
Regards,
PrecordialThump