Surprises in Evolutionary Tales
From spiders to crocodiles, animals rarely evolved the way they should have.
Hallucinating or classifying? The bizarre Cambrian creature Hallucigenia found in the Burgess Shale has a new home on the tree of life, Astrobiology Magazine announced (see also University of Cambridge press release): it’s an ancestor of velvet worms. Only an evolutionist could get excited by falsification (or is it rearranging chairs on the Titanic) —
“An exciting outcome of this study is that it turns our current understanding of the evolutionary tree of arthropods – the group including spiders, insects and crustaceans – upside down,” said Dr Javier Ortega-Hernandez, the paper’s co-author. “Most gene-based studies suggest that arthropods and velvet worms are closely related to each other; however, our results indicate that arthropods are actually closer to water bears, or tardigrades, a group of hardy microscopic animals best known for being able to survive the vacuum of space and sub-zero temperatures – leaving velvet worms as distant cousins.”
Stephanie Pappas at Live Science quoted a researcher who thinks the new classification rescues Darwinian gradualism from the Cambrian Explosion, but that’s a stiff shot of bluffing; calling this animal a transitional form does not answer the major arguments for design made by Stephen Meyer in his book, Darwin’s Doubt. Animations of Hallucigenia, with its weird back spines, can be seen on the Illustra documentary, Darwin’s Dilemma.
Comb jelly tales: In Current Biology, Marlow and Arendt try to sound optimistic about what evolutionists can learn by placing the complex ctenophores, or comb jellies, at the base of the animal tree of life, ancestral to sponges which seem much simpler. They admit it was a big surprise:
Analyses of the recently published genomes of the comb jellies Mnemiopsis leydii and Pleurobrachia (Figure 1A) now come as a particular surprise. Aligning the ctenophore predicted protein sequences to those of other animal groups and calculating the phylogenetic trees most consistent with the observed sequence divergence, both studies seem to find that the ctenophore lineage (and not sponges) represents the earliest branch of the animal tree of life. The authors argue by extension that the diverse array of ctenophore cell types (including neurons and muscle) must have arisen independently from those found in later branching animal lineages (cnidarians and bilaterians), resulting in “extensive parallel evolution of neural organization”…. While a finding supporting the independent evolution of nervous systems would indeed be remarkable, we have to step back and assess the implications of the new ctenophore data separately with regard to the two points mentioned above. What do we learn about the branching order of basal metazoans? And what does the complement of ‘neural genes’ present in ctenophores reveal about nervous system origins?
Spider convergence: Calling something a “breakthrough discovery” is a means of deflecting embarrassment when the discovery doesn’t support prior assumptions. That’s what PhysOrg did with the announcement that web weaving must have evolved independently in two different groups of spiders: “Researchers make breakthrough discovery about evolution of spiders and their webs.” The new phylogeny was published in Current Biology. A news item in Nature admitted that the new arrangement “reveals tangled evolution” and requires either putting the art of web-weaving in an unknown ancestor, from which several groups lost it, or believing that two groups arrived at the complex skill independently. Either scenario is distasteful. Whatever happens, “The new studies overturn decades-old dogma.” A second paper in Current Biology says the new phylogeny “rejects a prevailing paradigm for orb web evolution.”
Sibling luck: A paper in Geology puzzles over why ammonites died out but their close relatives, the nautiloids, survived the Cretaceous extinction. “One of the puzzles about the end-Cretaceous extinctions is why some organisms disappeared and others survived,” the paper begins. “A notable example is the differential extinction of ammonites and survival of nautilids, the two groups of co-occurring, externally shelled cephalopods at the end of the Cretaceous.” They could only guess: “Evidently, a broad geographic distribution may have initially protected some ammonites against extinction, but it did not guarantee their survival.”
See sea crocs croak: Scientists at Bristol University puzzled over the alleged disappearance and reappearance of marine crocodiles. Most crocodiles stick to fresh water but a few have ventured out into the ocean. Jerry Martin came up with the idea that temperature constrains their evolution, but his hypothesis could not account for one species:
Nevertheless, one fossil lineage does not appear to follow this trend. Jurassic metriorhynchoids did not go extinct during the cold spells of the early Cretaceous, unlike the teleosaurids, another group of marine crocodilians. Quite surprisingly, metriorhynchoids only disappeared a few million years later. This exception will certainly provide grounds for new research, particularly into how the biology of this group adapted to life in the pelagic environment.
Surprise survivor: On Live Science, Stephanie Pappas tells about a delicate lizard-like animal that, according to the evolutionary timeline, must have survived the extinction that wiped out the dinosaurs at the end of the Cretaceous. Related to today’s living Tuatara of New Zealand, the fossil rynchocephalian, found in a hard-to-get-to coastal site in Argentina, apparently survived over forty million years more. “We thought that they became extinct, but well, here they are,” the lead researcher said of the “surprise survivor.” And that’s not all he found: “Other animals found at the site, including mammals and turtles, appear to have survived the mass extinction as well,” he noted.
Scientists have so much fun keeping the Darwin story going. Every anomaly creates new joys, because it keeps them busy as storytellers. Millions of years; slow and gradual progress; a tree of life in research paradise – the mythology is wonderfully satisfying to the inebriated with Darwine. It’s a lovely fantasy that no facts can shake, even when it requires believing six impossible things before breakfast. Since Darwin’s theory has had such horrific effects on society, we can rightly dub their mythical tale Malice in Blunderland.