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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

Thursday, April 16, 2009

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.

1 comment:

  1. The problem with most people who fail to see evolution as a concept is the failure common to most humans -- that of linear thinking....

    Good post, Matt! Thank you for the content -- I'll be coming back for more...