by Piter Kehoma Boll
What would you think if someone came to you and said that your pet snail accidentally got pregnant and you’re the father? Or if you went to the doctor and he said to you “congratulations, you’re pregnant and the father is a sea urchin”. Of course you’d be proud, dontcha?
Well, if you think that’s a ridiculous nonsense, you’re quite right. But guess what? There’s a senior (i.e., very old) scientist claiming that such a thing happens in nature all the time! And what’s his name? Donald I. Williamson.
Born in 1922 (he’s 90!), he’s a British planktologist and carcinologist, already retired, of course. But at least from 1987 on he has been publishing a series of weird papers claiming that hybrids between different animal phyla happened many times during the history of animal kingdom.
All started, as already mentioned, in 1987, on his paper “Incongruous Larvae and the Origin of some Invertebrate Life-Histories” where he considers the huge differences between adults and larvae in many animals, at first mainly concerning echinoderms. His “revolutionary” idea is that larvae and adults evolved separately as different lineages of animals and later became a single species by hybridization. He claims it by initially citing works that suggest the possibility of horizontal gene transference between distantly related organisms, mainly caused by viruses carrying a small amount of their hosts’ DNA from one to another. So he apparently thought “If one can carry one gene from an animal to another, why couldn’t it happen with the whole genome?”.
Echinoderms, his first victims, are thought to have hybridized with hemichordates, so explaining why the larvae of both groups are so similar. By the end, he admits that he hasn’t made any research concerning all or most of the recent works on development and phylogeny of the targeted groups.
Here is important to cite a work by Švácha (1992) studying the imaginal disks in larvae of holometabolous insects (those with larva, pupa and adult stages). Imaginal discs are some regions of apparently undifferentiated cells in insects larvae and previously thought to be the source of most of the adult features not found in larvae, as well as being responsible for the replacement of some organs in larvae by new ones in adults, like the larvae’s antennae being replaced by new ones during the transition from one stage to another. Švácha noticed, however, that this actually doesn’t happen and that imaginal discs only help to develop larvae’s structures, but not replace them by new ones. That is to say, the adult form of insects does not come from a second “embryo” hidden inside the larva.
Of course Williamson ignored this paper and many others and in 2001 he brought another argument to sustain himself: a fallacy.
As you might or not know, the endosymbiosis theory suggests that some intracellular organelles, like mitochondria and chloroplasts, originated from bacteria associated to eukaryote cells. One then can state that the functions of intracellular organelles existed before the organelles themselves, so it was completely logical for Williamson to assume that the features of larvae existed before animals having larvae.”
Like if he was in a frenetic state, Williamson started to discharge loads of “perfectly possible” hybridizations between animal groups. To cite some:
- Turbellarian larvae came from Rotiferans
- Echinoderm larvae came from Hemichordates
- Tunicate larva came from Appendiculata (an old group comprising Arthropods, Annelids, Rotifers and others)
And to be even more bizarre, he suggests that the blastula in animals’ embryos came from hybridization with Volvocales, a group of green algae!
And as you can also see by reading his work, most of his references are his own previous works, obviously indicating a lack of interest in any REAL study trying to understand the origin of differences between larvae and adults. It is also worth noting that Williamson had some unusual phobia for the names of echinoderm classes, since the ending –oidea was to annoying for him to be seen in something other than a superfamily.
By 2006, Minelli et al. presented an interesting review of researches concerning the development of arthropods from larval forms to adults, where one of the possible explanations to the drastic change occurring in holometabolous insects larvae is nothing more complex that a kind of “neoteny”, i.e., when earlier stages of development last longer in an organism’s life cycle. In this case, the probable thing that happens is that the larva of holometabolous insects are kind of very developed and mobile embryos, nothing that weird, right? And guess what? In the whole review there is not even a single mention to Williamson, and we all can imagine why…
In this same year, Williamson attacks again with another paper, this time claiming that the Cambrian explosion happened due to a high number of hybridizations with larval transfer and, as in all of his previous works, uses the argument that “natural selection cannot explain such divergences between adults and larvae”. We can clearly notice that he completely ignores all recent publications concerning phylogenetics and genomics and, as it at least seems to me, ignores anything related to evolutionary theories other than Darwin’s The Origin of Species and Lynn Margulis works (to whom he appears to have some desperate passionate feelings).
An then again, in 2009, he comes with another article, this one at PNAS, entitled “Caterpillars evolved from onychophorans by hybridogenesis” where he persists in his absurd ideas, claiming that caterpillars arouse from a female moth being accidentally fertilized by a male onychophoran. and he still goes on ignoring anything related to molecular data, attacking Darwin’s and Haeckel’s ideas once more and citing only works that, by his limited point of view, could support in any way his incongruent ideas. All works published during these more than 20 years that he passed affirming the same nonsense, like a fanatic priest in a church, were left aside.
Anyway, this last work gained a higher repercussion than the previous ones and many scientists manifested their indignation with it, so that for two months the paper was held up from print publication, until finally appearing in print in the issue of November that year.
Now, seriously, how could it be possible that such a ridiculous idea was allowed to be published in this century, after all the serious researchers concerning phylogeny and ontogeny of animals?
Well, it was possible only for one reason: Lynn Margulis. She was the one that communicated the paper, via a submission route that allowed academy members of the United States National Academy of Sciences to manage the peer review of a colleague’s manuscript. But why would Lynn Margulis support such an idea from an old retired out of his mind “scientist”? I should say because she was pretty out of her mind too.
If you know Lynn Margulis, you also know that she was once a brilliant biologist with challenging ideas, helping to make the endosymbiosis theory to get known and eventually accepted to explain the origin of chloroplasts and mitochondria. But in her last years (she died on November 22, 2011) she started to attack well supported ideas in science in a kind of irrational way, like stating that AIDS isn’t caused by HIV.
When this last work was released for press, the same issue brought a challenge by zoologist Gonzalo Giribet and a paper by Hart & Grosberg rejecting Williamson’s ideas based on all molecular data already available that clearly indicate that holometabolous insects do not have onychophoran genes at all to explain such a BS.
Apparently Williamson prepared a briefly response, but it was not released to be published.
So after reading all this, I think anybody can understand why nobody can take him serious. Or would you ever believe that you can get pregnant by a jellyfish while swimming in the sea?
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Abbott, A., Brumfiel, G., Dolgin, E., Hand, E., Sanderson, K., Van Noorden, R., & Wadman, M. 2009. Whatever happened to …? Nature DOI: 10.1038/news.2009.1162
Giribet, G. 2009. On velvet worms and caterpillars: Science, fiction, or science fiction? Proceedings of the National Academy of Sciences, 106 (47), e131 DOI: 10.1073\pnas.0910279106
Hart, M., & Grosberg, R. 2009. Caterpillars did not evolve from onychophorans by hybridogenesis Proceedings of the National Academy of Sciences, 106 (47), 19906-19909 DOI: 10.1073/pnas.0910229106
Minelli, A., Brena, C., Deflorian, G., Maruzzo, D., & Fusco, G. 2006. From embryo to adult—beyond the conventional periodization of arthropod development Development Genes and Evolution, 216 (7-8), 373-383 DOI: 10.1007/s00427-006-0075-6
Švácha, P. 1992. What Are and What Are Not imaginal Discs: Reevaluation of Some Basic Concepts (Insecta, Holometabola) Developmental Biology, 154, 101-117
Williamson, D. 1987. Incongruous larvae and the origin of some invertebrate life-histories Progress In Oceanography, 19 (2), 87-116 DOI: 10.1016/0079-6611(87)90005-X
Williamson, D. 2001. Larval transfer and the origins of larvae Zoological Journal of the Linnean Society, 131 (1), 111-122 DOI: 10.1006/zjls.2000.0252
Williamson, D. 2006. Hybridization in the evolution of animal form and life-cycle Zoological Journal of the Linnean Society, 148 (4), 585-602 DOI: 10.1111/j.1096-3642.2006.00236.x
Williamson, D. 2009. Caterpillars evolved from onychophorans by hybridogenesis Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0908357106