Misconceptions about evolutionary theory

Part Two: Where are the transitional species?

I'm frequently asked, "if evolution is real, where are the transitional species?" The proper answer should be: If you want to see a transitional species look in the mirror.

One of the many wrongheaded ideas out there is that evolution runs from point A to point Z and ended at Homo sapiens. Evolution, as I pointed out last week, isn't directional AND it doesn't have an end. Everything is a transitional species. Had there been any Austrolopithicene anthropologists they wouldn't have thought to themselves "we are a transitional species on the road to a more advanced hominid." How can we know what is a "transitional species" if we don't know what is coming next?

I'm certain that answer won't satisfy everyone, so I'll do my best here to provide modern day examples of species in transition.

My favorite is the recent discovery of a band of chimps who have learned to not only use, but create spears. They use them to kill bush babies. This new technology will create more and easier food for members of this band, so they should outreproduce other bands of chimps, spreading this behavior more widely. More importantly, perhaps, is the fact that within the band some of the chimps will have musculature that makes them better at using spears, or better vision, or maybe the ability to make spears faster. If those chimps are lucky enough to survive and pass those traits along at a higher rate than other chimps I'd be willing to be that in another few hundred thousand years we'd be looking at a species of ape that we don't have today.

Another example of things in transition are organs. Evolutin deniers often use the eye as an example. "What good is half an eye?" It turns out there are all kinds of uses for a less than perfect 20/20 vision eye. At this point I'd point out that thinking that our eyes are the pinnacle of evolution is painfully anthropocentric. If I could choose I'd trade my eyes in for raptor eyes anytime. If we were to travel back in time several hundred million years to the time when the first predators emerged we'd find two opposing reasons why it would be useful to have light responsive protiens in our skin. If I'm a defenseless herbivore a really good survival strategy would be to hide under a rock somewhere. But how do I know if I'm hidden? If I can "feel" light I know I'm not hidden. A predator would have this advantage in reverse, if they are cruising through some primordial goo and can tell the difference between nothing in front of them and something in front they would know what direction to go in. In either event, be they predators trying to hide or hunters looking for something to eat its pretty obvious that a simple light detector would be valuable, but the ability to differentiate even more would be more valuable still.

The picture at the top allows for two important points, the first is that the fossil record shows transitional species. Someone asked me to show transitional species from bacteria all the way up to human beings. As you look through older sets of rocks the species are there. Precambrian rocks show only single cell critters, Cambrian rocks show somewhat larger and more complex plants and animals. Everyone here knows the rest of the story. Someone once said that a beautiful elegant theory can be wrecked by a single ugly fact. If somebody was to produce a fossil showing human footprints alongside Trilobites, or a spearpoint embedded in a T-Rex skeleton, evolutionary theory would fall down in an instant. So far it hasn't happened. The second point is that the diagram is terribly misleading because it looks like a ladder. in fact each of those horse progenitors had several descendants. The diagram should look much more like a bush or a cobweb than a ladder.

One final story, as a kid one of my favorite prehistoric creatures was the Dimetrodon, I always thought the sail fin was really cool. But what was even cooler was a new trait that makes the Dimetrodon one of the more significant "transitional species" It was the first creature to sport multiple types of teeth. Before Dimetrodon came along animals had either sharp pointy teeth or dull crushing teeth. Even though this really neat sail backed beast was clearly not a mammal, it was one of the first steps along the way, it is likely that the fossilized creature above is a distant ancestor of all of us reading my blog today.

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….