About two years ago, I called attention to a bizarre paper in The Proceedings of the National Academy of Sciences (PNAS) by Donald Williamson, claiming that the life cycle of Lepidoptera, with a distinct caterpillar and adult stage, was produced by the hybridization between an ancestral butterfly (lacking a caterpillar stage) and an onycophoran (a velvet worm, the presumed ancestor of the caterpillar). This was palpably ridiculous since DNA sequencing would have revealed such a strange agglomeration immediately.
As I expected, that paper was thoroughly debunked by several people, including Michael Hart and Rick Grosberg, and now carries no weight. It also shook up things at the journal, because the paper’s editor, Lynn Margulis, appeared to have violated editorial procedure by submitting only the good reviews and ignoring the bad ones.
A site called RetractionWatch, of which I was unaware, has reported that yet another paper by Donald Williamson—one on the same topic—has been formally retracted.
Retraction Watch has saved the original article, which you can find here. Williamson’s thesis is that complex life cycles of animals, involving larvae that are very different from adults, involved the acquisition of foreign genomes through either symbiogenesis (engulfing of one species by another, as in the formation of mitochondria from nommed bacteria) or hybridogenesis (two completely different species hybridize, as in Williamson’s previously retracted PNAS paper). Here’s the abstract of the retracted paper:
My larval transfer hypothesis asserts that mature adults became larvae in foreign animal lineages by genome acquisition. Larval genomes were acquired by hybridizationwhen sperm of one animal fertilized eggs of another animal, often remotely related. There were no larvae in any phylum until the classes (and, in some cases, the orders) of that phylum had evolved. Since larvae were acquired by hybrid transfer, they are not directly related to the adults that metamorphose from them. The widely accepted classification that associates echinoderms and chordates as deuterostomes, and annelids and molluscs as trochophorates or lophotrochozoans, is flawed. Symbiogenesis, the generation of new life forms by symbiosis, accounts for the discontinuous evolution of eukaryotic cells from prokaryotes. Hybridogenesis, the generation of new life forms and life histories by hybridization in sexually reproducing animals, occurred at all taxonomic levels from species to superphyla. Not only were larvae acquired by transfer from foreign adults from the late Palaeozoic to the present, but also complex animals were generated from simpler ones by this process in the Cambrian explosion, and organ systems were transferred between remotely related animals. There are several types of evolution. Symbiogenesis and hybridogenesis are saltatory genome transfer processes that dramatically supplement the gradual accumulation of random mutations within separate lineages described by Darwin.
The problem, of course, as Hart and Grosberg (and others) pointed out in their critique, is that Williamson’s original hypothesis has already been refuted by genetic analysis: butterfly genomes should show significant amounts of DNA more closely related to onycophorans than to other butterflies, and they don’t. That’s also the case for the present paper at all: no phylogeny supports the idea of larvae arising by symbiosis or hybridogenesis.
Williamson’s new paper has been not only retracted, but completely effaced: here’s what you get when you go to the article’s pdf:
And the journal’s editor, David Richardson, issued only a terse remark:
I am not willing to discuss this matter except to say that it did not involve any matter of wrong-doing by the author, simply that a significant amount of the information in the paper closely duplicated that published earlier without sufficiently addressing previous concerns about the significance of particular findings.
Can you imagine a similar retraction issued when a claim of theology was falsified? It’s as if Albert Mohler admitted that he now denies the factuality of Adam and Eve in light of new genetic findings.
At any rate, this shows once again that the truth will out in science. And it also refutes claims by Lynn Margulis and others that hybridization and symbiosis are more than just important events in the creation of evolutionary novelty—as they were indeed for things like chloroplasts and mitochondria—but are ubiquitous, with that ubiquity constituting a refutation of the tenets of modern evolutionary theory.