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I have been a student of natural history as long as I could walk. Since graduating from Humboldt State University in 1985 I've been fortunate enough to get paid to do something that I'd do for free

Monday, April 13, 2009

Misconceptions about evolutionary theory

Part 1. The curious of Cuscuta- Can evolution run in reverse?

Over the next several weeks I'm going to post blogs addressing the common misconceptions about evolutionary theory. I learned a long time ago that trying to change the minds of either the die hard evolutionary thinkers (I'm one) or a creationist is simply not going to work, but my hope is that I can shed some light on what we actually believe, rather than the straw man that is usually created, then knocked down by the creationist debaters. The first of the many false arguments made is that evolution is a one way street, leading from simple bacteria to man kind.

Any casual observer would note that there are a lot more bacteria than anything else on this globe, so its hard to argue that everything evolves in a straight line. The old saw "if we evolved from monkeys, why are there still monkeys?" should still apply. "if we evolved from bacteria, why are there still bacteria?"

I'd like to make my argument with Cuscuta (commonly called Dodder, or devils weed). Cuscuta is a common sight in dryish areas in Southern California (and around the world in similar environments) At first sight it looks as if someone has poured spaghetti all over the brush living on hillsides. On closer inspection we find a very simple plant, with long stringy stems and almost no structural support, roots piercing into the host plant (dodder has no photosynthetic ability, and relies entirely on its host plant for survival.) and flowers or fruit depending how late into the season it is. That’s all, no thorns, chloroplasts, leaves, bracts, chemoattractants nothing….. A very simple plant indeed. At first blush one might assume that this would be an ancestral sort of plant. First a simple parasite, then later the leaves would evolve and perhaps the fruit or flowers would become showy to attract pollinators or seed dispersers. The common vision of evolutionary theory would seem to support that idea. Evolution connotes “onward and upward” right?? In fact it doesn’t , evolutionary theory states only that species change over time in response to the combination of environmental changes and genetic drift. It turns out the Dodder is a very highly evolved (if simple) plant. It is most closely related to morning glory, another plant that makes its living climbing on other things. Apparently somewhere in the distant past a common ancestor stuck its roots into the plant it was climbing on and “discovered” that it was easier to make a living stealing from a plant that did all the hard work of bringing moisture from the ground and creating food via photosynthesis. Over time those plants that did less work growing their own food, and thus making more seeds (Dodder is a prodigious parent) outreproduced the plants that “played fair” until finally we have the Dodder of today, entirely helpless without a host plant, but, if you look closely at the flower structure, or DNA, the ancestry is there clear as day.

The point of this little essay is just to demonstrate that evolution does not have to make increasingly complex organism, it can, and most often does, keep things very simple. That’s why most life on earth is still bacteria. It takes a great deal of luck to rise from the goo, we should feel honored….

1 comment:

  1. What? You mean the earth didn't begin six thousand years ago? Sorry - just kidding.