Last year Russell Garwood, a paleontologist at the University of Manchester (ergo Matthew Cobb’s colleague), published a paper in Nature Communications along with several collaborators (reference below). The results were striking: fossil harvestmen (arachnids sometimes known as “daddy long-legs”) from 305 million years ago are strikingly similar to modern species—so similar, in fact, that they can be identified as members of existing lineages (suborders). In other words, this group shows a striking morphological stasis: a lack of evolution of at least the fossilizable parts of the body. I hasten to add that some body parts, like the genitals, were not preserved, and that of course there could have been substantial evolution of biochemical systems, physiology, and internal anatomy that can’t be seen in fossils. Nevertheless, we have few groups that show such profound stasis. And 305 millon years ago is a long time ago: that’s around the period when the lineage that produced modern reptiles branched off from its amphibian ancestors.
Why some groups like this are morphologically conservative isn’t known, though there are speculations (i.e., their environment didn’t change much over millions of years). Or they could simply be one tail end in a Gaussian distribution of evolutionary change. Such “living fossils” are the subject of Richard Fortey’s new popular book, Horseshoe Crabs and Velvet Worms: The Story of the Animals and Plants That Time Has Left Behind.
At any rate, the paper is only partly the subject of this post, but let’s look at the fossils first. Here’s how well preserved the specimens were (they were found in France). Click to enlarge. These are computer reconstructions from high-resolution X-ray microtomography, a method that can produce a three-dimensional reconstruction without destroying a specimen:
Here’s a reconstruction of two fossil species:
And here’s a comparison of the dorsal (back) side of a fossil with its modern relative, showing how similar the external anatomy has remained over three hundred million years:
As we’ll see below, Garwood is rightfully peeved that creationists are using his paper as evidence against evolution, saying, “See, things didn’t evolve, even though Darwinism predicts they will!” (The Turkish creationist Harun Yahya specializes in this trope.)
But “living fossils” don’t violate any of the tenets of neo-Darwinian evolution. That theory doesn’t tell us that species must evolve, only that they will in general undergo morphological, biochemical and physiological evolution when conditions change. And there is always a certain amount of molecular evolution going on due to genetic drift (I’d bet a “stasis creationist” thousands of dollars that if we could sequence the DNA of those fossil spiders, it would be substantially different in non-coding positions from that of its modern relatives). Neo-Darwinism doesn’t predict how a species will evolve in the future, or whether it will evolve at all. So living fossils don’t count as evidence for creationism. And, of course, against creationism stand the vastly larger greater of lineages that did evolve, producing among other forms the transitional species that creationists must to sputter and sweat to explain. Indeed, I’m surprised that Garwood is surprised, since American evolutionists are used to this kind of distortion.
Garwood’s just expressed his frustration about the creationist misuse of his work in a column in Nature: “Reach out to defend evolution,” in which he urges scientists communicate with the public to prevent misunderstandings of evolution. Here’s a snippet:
We don’t know why harvestmen are such a good example of morphological stasis; but the fact that they are in no way undermines evolution. Rather, it indicates that further work is needed and encourages such work. Yet knowing that unknowns will be presented as evidence of a designer does make writing up the results a potential minefield.
We should not let creationist pressure alter the way we do science — the day that researchers become reticent about highlighting inconsistencies and uncertainty would be a dark one. But equally, we are not helpless when it comes to countering creationist disinformation based on our results. I believe that science would benefit greatly if we did more outreach when we publish and publicize our research.
Direct debates with creationists are risky. Organized discussions only support the ‘evolution is in crisis’ lobby. However, a proliferation of online tools means that we can make accurate information freely available to those interested enough to look for it. Arizona State University’s Ask a Biologist web page has fielded more than 25,000 questions from students and teachers since it launched in 1997.
If research is to appear that will attract an obvious creationist interpretation, an accompanying blog post could explain the work and highlight flaws in any anti-evolution attacks. Sites such as the Natural Environment Research Council’s Planet Earth Online and the Palaeontological Association-sponsored palaeontologyonline.com provide researchers with vehicles for one-off posts. Publishers can do more, and could offer online summaries in non-technical language, written by the researchers. The open-access journal Palaeontologia Electronica already does this.
So, Russell, here is the “blog”* post you wanted. But don’t be so quick to assume that pieces like this will change any minds, for the opponents of evolution won’t, by and large, be convinced by them. They are blinded not by ignorance but by religion. Perhaps you wouldn’t be so surprised if you had grown up in the hyper-religious United States.
*”blog” is Garwood’s word for “website”
Garwood, R. J., J. A. Dunlop, G. Giribet and M. D. Sutton. 2012. Anatomically modern Carbiniferous harvestmen demonstrate early cladogenesis and stasis in Opiliones. Nature Comm. 2:44 doi:10.1038/ncomms1458