This time it’s personal, because the creationists are dissing fly research!
Yesterday I described a new paper by Wiegmann et al. on the family tree of flies (Diptera); the reference and free link are at the bottom. It’s a good piece of work, and resolved several questions that had long puzzled students of fly biology.
But the creationists—that is, the oxymoronically named Institute for Creation Research—have got their dirty mitts on the paper, and have published a “critique” (read “distortion”) of the results in a piece called “Periodic table of flies is guesswork, not science.” Here’s a screenshot: note their LOLzy slogan at the upper right:
You can read their short critique on the ICR site. Their basic claim is that there’s no scientific basis for constructing phylogenies (family trees): it’s all guesswork, and basically a scam by scientists who use unreliable and constantly changing methods to buttress their “faith” in evolution. The ICR concludes:
And in all of the research conducted to fit fly data into a preconceived notion of fly evolution, the researchers have yet to find any data that challenge the concept that flies were created.
Of course one can wonder why the Creator, in His ineffable wisdom, made flies and mosquitoes to torment and kill the object of creation.
What I’m going to do is put up an analysis by a professional systematist of how duplicitious this ICR article is. Christian creationists won’t, of course, be swayed by scientific counterarguments, but perhaps it will be instructive to see how creationists distort data in a field that’s unfamiliar to most laypeople: systematics.
The analysis below the line is by my friend Phil Ward, a professor in the Entomology Department at the University of California at Davis. He works on ant systematics, but is also deeply knowledgeable about evolution in general. I’ve asked him to respond to the ICR piece in a way that biologically interested laypeople could understand. Many thanks to Phil for the following (the indented parts are taken from the ICR piece):
The Wiegmann et al. paper is the most comprehensive study to date on the evolutionary history of two-winged flies or Diptera. It provides a well supported “backbone” phylogeny of this large and diverse group of insects, based on analysis of a newly generated and quite substantial molecular data set. I think that any insect systematist would consider this a very significant contribution to the field. The criticisms and distortions of the study by the Creation Research Institute (CRI) are laughable and are hardly worthy of serious consideration—except that they will be taken seriously by some misguided souls.
At the outset the CRI article mischaracterizes the Wiegmann et al. study as one in which the investigators attempted to determine “which types of fly likely evolved into other types”. This exemplifies a fallacious view, apparently widespread among creationists, that evolution posits the origin of one extant kind of organism from another extant kind (e.g., that chimps evolved into humans).
The procedure for building evolutionary trees requires many assumptions, and one of them is the decision of which fly best represents the “first” flies at the “root” of the fly evolutionary tree.
Again this reflects a misunderstanding of how the phylogenetic analysis was carried out. The root of the tree (the common ancestor of all flies) was inferred by including in the data matrix other non-dipteran insects belonging to a more inclusive group known as the Endopterygota (these are insects with holometabolous development, that is to say, those whose life cycle encompasses four stages: egg, larva, pupa and adult). Wiegmann et al. did not arbitrarily “decide” that the strange flies belonging to the family Deuterophlebiidae would be at the base of the tree as sister to all other Diptera. This emerged from the phylogenetic analysis that included both ingroup taxa (flies) and outgroup taxa (non-dipteran holometabolous insects). Moreover it would be incorrect to say that the study concluded that Deuterophlebiidae represent the “first” flies – they are simply an old, species-poor lineage that is sister to all other Diptera. They no more represent the ancestral fly than the duck-billed platypus (or echidna) represents the first mammal.
Many prior evolutionary tree studies have amply demonstrated that the different “trees” that can be built from the same genetic and structural data are as numerous and varied as the investigators who construct them.
The estimation of evolutionary trees is affected by the quality of the data and the assumptions that accompany the analyses. But as we accumulate more data (particularly abundant and informative DNA sequence data from the genomes of different species) there is increasing stability and consensus about the major features of the tree of life. Of course there remain some contentious areas, especially the placement of old and long isolated branches in the tree, but the progress that has been made in the last decade is truly remarkable.
Despite the use of scientific-sounding words like “phylogenomics”—which attempts to reconstruct the supposed evolutionary history of an organism using its gene sequence data— this constantly changing structure is a clear sign that the trees are subjective inventions that only masquerade as observable “science.” The new fly tree shows no signs of breaking this mold.
As if the modification or replacement of hypotheses is a bad thing! Actually the new fly tree confirms many long-standing traditional views about dipteran phylogeny. It provides strong evidence that many kinds of flies previously delimited by morphological attributes are in fact monophyletic groups (a monophyletic group is an assemblage of species that comprises their most recent common ancestor and all its descendants). At the same time the study generates a number of novel findings, revealing for example that the family Drosophilidae (containing Drosophila) is closely related to two rather odd groups of flies that parasitize bees and other insects. Other contentious questions about fly phylogeny are addressed and provisionally answered. More generally, the Wiegmann et al. study provides a clearer picture of the changes in life history traits and rates of diversification that have occurred during the 260 million year history of these fascinating organisms.
Finally Wiegmann et al. point out that there is still much to be learned about the tempo and mode of fly evolution, especially in the species-rich group known as Schizophora which radiated in the early Tertiary (65-40 million years ago). This will require much more intensive sampling of flies and genes. How much more satisfying and intriguing than “Biblical, Accurate, and Certain”!
Wiegmann, B. M. et al. (many authors). 2011. Episodic radiations in the fly tree of life. Proc. Nat. Acad. Sci. USA, doi:10.1073/pnas.1012675108