Evolution News From Down Unda
Australia and New Zealand contain some of the most unique and distinctive flora and fauna in the world. Evolutionary explanations for some of these animals and plants have come to light in the press recently.
- Koala: Did you know there are extinct koalas? Science Daily reported about work by Aussie biologists to understand the evolution of the koala, based on recently discovered skulls of extinct varieties. They infer that the continent was wetter when those species lived. “The team led by Dr. Louys found that the chewing apparatus of the living koala is much more specialized than its fossil forebears, including adaptations for more powerful bite forces and the ability to shred the tough leaves of the eucalypts [sic] that are the mainstay of its diet.” The middle ear bones, though, have changed very little. The scientists interpreted this, “This indicates that the specialized loud and complex vocalizations of living koalas – a trait unusual among marsupials – likely have an ancient origin.”
The article ended with a description of how evolution works: “The study therefore shows that the chewing apparatus and hearing adaptations in living koalas evolved at different times and under different environmental circumstances, an indication that adaptations, even in the most specialized animals, may have disparate origins and evolve in mosaic fashion.” Another article on Science Daily inferred from the fossil teeth that “ancient koalas may have been loud and lazy, but they didn’t chew gum.”
- Platypus: Talk about a mosaic animal: as mentioned briefly last month (11/16/2009, bullet 10), researchers at the University of Adelaide have been studying the genes of the duck-billed platypus. 28 papers on monotremes (platypus and echidna) were published recently in the Australian Journal of Zoology and Reproduction Fertility and Development, five of which promised to “shed new light on the extraordinary complex platypus sex chromosome system.” This was not a case of shedding light on evolution itself, though: “We discovered that a remarkably organised mechanism must exist in platypus, where sex chromosomes from one end pair first and then they go down the sex chromosome chain, just like a zipper,” said the lead author. “There is nothing random about it.”
As for platypus evolution, he said that their findings “have given us valuable clues about the evolution of Y chromosomes in all mammals, including humans,” but the article failed to mention what those clues were, or if they suggested an increase in genetic information. He also said he expected “these results to make a major impact in the field of monotreme research and mammal evolution.”
- Wollemi Pine: The discovery of Wollemi pines alive in a remote canyon of Australia 150 km northwest of Sydney was one of the big stories of 1994, because they represent a “living fossil” species from the age of dinosaurs, thought to have been extinct for millions of years. PhysOrg reported that the genome of the Wollemi pine has been sequenced by students at the University of New South Wales. Not much was revealed about what the genome shows yet. “The students’ preliminary findings show that the Wollemi chloroplast DNA is unique but shares some features with other pines such as the Kauri and Norfolk Island Pine,” throwing doubt on the meaning of unique. “Further analysis of the data,” the article promised, “will provide clues to the evolution of the Wollemi and other pines.” Nothing was said about how these living trees, possessing low genetic diversity, “survived 200 million years of shifting continents and changing climates.” If they were so hardy for so long, why are humans fighting to protect them from extinction now? “The Wollemi is being protected from extinction by secrecy surrounding the locations of the wild populations, and by widespread cultivation of the pine in Australia and around the world,” the article said.
- Marsupial evolution: An article on Science Daily said that researchers from the University of Florida traced marsupials back to the death of the dinosaurs and found “evidence to support North America as the center of origin for all living marsupials.” So did kangaroos hop over the sea? Their answer would be that they weren’t kangaroos then, but primitive opossum-like creatures that were the ancestors of all marsupials. South America and Australia were connected at the time of the extinction of the dinosaurs 65 million years ago, they would also point out.
Their evolution story, however, rests on very fragmentary evidence. The researchers examined one opossum skull from Wyoming, claimed to be 55 million years old, and “two 30-million-year-old skeletons of Herpetotheriidae, the sister group of all living marsupials.” Those data points apparently were deemed sufficient for the team to draw evolutionary conclusions: “Based on fossil evidence from the skull and two skeletons, the study’s authors concluded the evolutionary split between the ancestor of opossums and the ancestor of all other living marsupials occurred at least 65 million years ago,” they said. Somehow, all the North American marsupials went extinct, but when a land bridge opened back up at Panama, opossums came back to the north and became one of the most commonly observed mammals in North America.
If the above story is to be believed, North American marsupials never got much past the look of the 55 million year ancestor of the opossums: “You would probably recognize it as an opossum, but it wouldn’t look quite right,” the lead author said. In that same time, however, the marsupials that made it to Australia evolved into kangaroos, Tasmanian devils, wombats, koalas, marsupial lions, marsupial moles, marsupial squirrels, and (of course) opossums – some 200 species of the world’s 334 marsupials. Put beside one another, they would look like a fair representation of many animals in the zoo – except the females would have pouches instead of a placenta.
It is clear that evolution as an explanatory device serves only as a storytelling framework. Toss in millions of years here, tens of millions of years there, hundreds of millions over yonder. Evolution can produce rapid change (from opossum to kangaroo) or incredible stasis (12/26/2006). Opossums will wander into one continent and evolve into kangaroos and marsupial lions, but on another continent, in the same amount of time, will stay looking pretty much like opossums (read The Convergence Concoction to see how incredible this evolutionary explanation is). Conifers will give rise to the vast array of flowering plants in 200 million years, but some of them will stay completely unchanged, leaving no trace in the fossil record for millions of years, till they are discovered alive and well today.
The framework is only limited by the imagination and faith of the evolutionary biologists. They are convinced they are doing science when weaving these fantastic, incredible tales based on a fragments of bone and teeth. The framework is reinforced by the sheer number on the Darwin Party roster. All the Know-Nothings (02/22/2008 commentary) who have bought into the framework provide one another with comaradarie, fellowship and emotional support. Their millions of years are like Monopoly money that can be traded and exchanged according to the internal rules of the game they have set up for themselves. That description is apt; the quote after this entry described today’s science as the perpetuation of knowledge monopolies. These factors permit self-fulfilling prophecies and self-reinforcing commitments that allow evolutionary biologists to feel comfortable with Groupthink, lest they see with their eyes, and hear with their ears, and recognize their folly, and repent of following the imagination of their own hearts (01/17/2007 commentary), while pretending to “shed light” on reality.
G’day anyway, and Merry Christmas to all our loyal readers down unda (picture). Try not to overdo the suntan while the New Yorkers freeze up yonda.