David MacMillan: Understanding Creationism, Part IV: The Predictive Power of Evolution

David MacMillan's fourth post on being an ex-creationist is over at The Panda's thumb and in this one, he writes about why it is so hard for those with the YEC perspective to understand the evolutionary biological concept of “transitional” fossil. He writes:

Young-earth creationists believe that all life, living and fossil, can be grouped into a series of families – they call them baramins, a made-up Hebrew word for “created kinds” – which all existed together at the same time from the very beginning. They use this completely artificial understanding of our planet’s biosphere in generating their concept of a “missing link”: in order for something to be a “true” transitional form under their model, it would have to be something halfway between two separate created “kinds”. Because they automatically assign every species to a particular created kind and only to that created kind, their “transitional form” is something that could never exist.

The usual parodies of evolutionary transitional fossils, like Ray Comfort’s infamous crocoduck, are openly tongue-in-cheek. But because creationists see all animals as belonging to individual, immutable kinds, they represent evolution as “change from one ‘kind’ to another” claiming that evolution predicts we should see transitions between their “created kinds”: for example, a fossil that is midway between a dog and a cat. Just as with living species, all fossil species are placed within strict “created kinds”, allowing creationists to maintain the illusion that nothing is ever “in-between”.

This is only one aspect of the problem. The other problem, mentioned in Young's third post in the series, is the mistaken belief that evolution is entirely vertical and that there is only direct ancestry and not collateral ancestry. With this understanding, one species directly leads to another species and so on. That Archaeopteryx may not have been ancestral to modern birds must mean that we have a gap in the fossil record. These “gaps” must mean that there are problems with evolutionary biology.  With created “kinds,” the species related to Archaeopteryx simply create gaps of their own.  It is difficult to penetrate this logic. 

Todd Wood and the Neandertal Genome

Todd Wood has written a post on the Neandertal genome and what it means for the origins of modern humans. His post is called the Neandertal Non sequitur and the title refers to his reaction to Fuz Rana's analysis over at Reasons to Believe. But that is not subject of this post.

I should note that he is almost alone in spelling the word "Neandertal" the way the Germans have been spelling it for the last hundred years. Hats off. On to the post. He writes:

In my hominid baraminology paper, I merely cite Darwin's claim that similarities form a pattern that looks like a genealogy, thus supporting the inference of common ancestry.

I've been criticized for this stance, but I'm not going to address those criticisms today. I'll just assert that I'm correct, which I am. The fact of similarity is easy to account for. Being created by one God would be a good reason for some degree of similarity to exist. Likewise, being created to occupy the same world or to participate in the same ecosystem would also necessitate some biological similarity. These types of considerations could explain why all living things use the same basic biochemical building blocks (amino acids, nucleotides, etc.), for example.

And if that were the only thing that supported common ancestry, that would be a defensible position. But it is not. One of the principle reasons that the trees derived from genetic data hold up is that we can look at the fossil record and see corroboration of where those the branches lie. It is not just that we have a record of some Neandertal genes being present in the modern genome. We also have the observed evidence of the morphological similarities between Neandertals and modern humans. In addition, in many places in which these two hominid forms appear, their behavior is hard to distinguish. There are countless other examples.

Genetic evidence suggests a diversification between fish and tetrapods several hundred million years back. Lo and behold, we find fishapods in the Devonian—animals, to quote Sir Arthur Keith, "In the throes of transition." Put simply, the further we go back in the fossil record, the fewer branches we find. This is exactly what you would expect with universal common descent based on evolution. Similarity might be easy to account for in the creationist perspective. When the fossil record is factored in, it is not.

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Douglas Theobald and Universal Common Ancestry

Douglas Theobald has written a technical paper on a test for universal common ancestry. The text of the paper is posted at Panda's Thumb, which also gives a short synopsis. Mike Steele and David Penny have also broken down the article here. They write:

So what is the signal in sequence data that provides the evidence for common ancestry? In essence, it is site-specific correlations in the amino acids between different species. These correlations fall off as the coalescence between lineages in a tree becomes deeper in the past, but if there are sufficient data, the correlations' cumulative significance becomes statistically strong. Conversely, if two lineages have completely separate origins, correlations between amino-acid site patterns in the corresponding two extant species vanish.

This article basically suggests, if I understand it correctly, that if species were independently created (think: *poof*), they would show smaller correlations in the coalescence results. This indicates that the further back you go, the sequence data shows common descent. As you go back in the fossil record and compare that to the genetic data of different species, certain protein sequences remain in common. Hat tip to Panda's Thumb.

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