The presence of “gaps” in the fossil record is one of the main arguments creationists use against evolution. The transition from Coelurosaurian dinosaurs to birds is one such purported gap that creationists like to harp on about. Evolutionary biologists would argue that Archeopteryx fills this gap quite nicely, but this is disputed by creationists, who argue that Archaeopteryx is a true bird and not a transitional form.
A recent study by Phil Senter of Fayetteville State University in North Carolina, published in Journal of Evolutionary Biology, takes another look at the evolution of Coelurosauria but with a twist. Senter takes on the creationists on their own terms, using a statistical method developed by creationists to visualise morphological gaps in the fossil record, to show that actually, there aren’t any morphological gaps in the fossil record between basal birds (including Archeopteryx) and a range of non-avian dinosaurs. These findings will come as no great surprise to evolutionary biologists who have long accepted that birds evolved from dinosaurs and that Archaeopteryx has both bird-like and dinosaur-like features. However, Senter’s rational for doing this study was that if you can demonstrate evolutionary relatedness between species under creationist’s criteria, then they will be obliged to accept the results.
This study is an interesting exercise, but I’m not sure that it really adds a whole lot to the creation vs evolution debate. Firstly, I’m a little uneasy about the methods he uses. If they are not sound scientific methods, what does it matter what they show?
The methods Senter uses were adapted from the field of baraminology, a branch of creation science in which organisms are classified according to a creationist framework. Baraminologists believe that each “kind” of organism was created independently and subsequently diversified – and view morphological gaps between taxa as evidence that the taxa were created separately. Rather than use established methods for measuring morphological relatedness, the baraminologists seem to have developed their own methods, which don’t seem to be in use outside of the creation science literature.
I’m not a statistician, or a paleontologist, so I don’t know much about these methods, but they seem to be similar to established methods for analyzing multivariate statistics, like principal components analysis and multidimensional scaling. One of the methods, ANOPA (Analysis of patterns) is even published in a regular scientific journal. However, a quick search of the Web of Science shows that this paper, published in 2004, has been cited zero times (with the exception of Senter’s paper) suggesting the method hasn’t been picked up by mainstream scientists. And according to this critique of the method, there are good reasons why not, not the least of which is that there seems to be no statistical basis for identifying discrete groups in the data. A similar method, that Senter applies to his data is classic multidimensional scaling (CMDS), as implemented in a software program developed by creationist Todd Charles Wood. Multidimensional scaling is a standard statistical method, but here it uses a creationist measure of “baraminic distances” – which only appears in the creationist literature and isn’t used in standard paleontology.
A second problem with this exercise, is that now that Coelurosaurian dinosaurs and birds have been shown to be morphologically continuous using the creationists criteria, what is to stop the creationists just moving the goalposts and calling Coelurosaurian dinosaurs and birds a single “created kind”? Also if evolutionary biologists use these method on other groups and find morphological discontinuity, do they then have to accept this as “evidence” for creation?
The problem with the fossil record is that (a) fossilization is rare, so absence of evidence is not evidence of absence, and (b) new fossils are found all the time, so what looks like a gap in the fossil record at one point in time may be filled later on. Senter demonstrates this really well in his paper, by re-doing the analysis based on what fossils were known at particular time points. Using this time-series he demonstrates that up until around 2000, there were significant gaps in the fossil record for coelurosaurians. However, with an explosion of new fossils in the past 10 years, these gaps have all but been filled. The same is true for many other groups, including basal chordates, bony fishes, turtles etc. Senter comments in the discussion
the recent explosion in the filling of fossil gaps should give creationists pause, for any such gap-filling is a serious challenge to creation science.
SENTER, P. (2010). Using creation science to demonstrate evolution: application of a creationist method for visualizing gaps in the fossil record to a phylogenetic study of coelurosaurian dinosaurs Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2010.02039.x