Carl Zimmer is one kinky dude—he has a new article on sexual cannibalism in the NY Times, and his expansion on the topic in his blog is also darned interesting, focusing on the scientific duels fought over adaptationism and exaptations in explaining the phenomenon.
Good news for Minnesota! Minnesota Citizens for Science Education has been officially launched. This is a new advocacy group with the goal of promoting good science education in our state. Specifically—
A scientifically literate population is essential to Minnesota’s future. To that end, Minnesota Citizens for Science Education (MnCSE) will bring together the combined resources of teachers, scientists, and citizens to assure, defend, and promote the teaching and learning of evolutionary biology and other sciences in K-12 public school science classrooms, consistent with current scientific knowledge, theories, and practice.
If you’d like to be more involved, join the group. Browse the personal statements of the science advisors. Come on down to Science Education Saturday at the Bell Museum, on 11 November.
Oh, and if you like the logo, buy it on a t-shirt or coffee mug.
We’re only sorta bilaterally symmetric: superficially, our left and right halves are very similar, but dig down a little deeper, and all kinds of interesting differences appear. Our hearts are larger on the left than the right, our appendix is on the right side, even our brains have significant differences, with the speech centers typically on the left side. That there is asymmetry isn’t entirely surprising—if you’ve got this long coil of guts with a little appendix near one end, it’s got to flop to one side or the other—but what has puzzled scientists for a long time is how things so consistently flop over in the same direction in individual after individual. There has to be some deep-seated mechanism that biases developmental events to favor one direction over the other. We know many of the genes involved in asymmetry, but what is the first step that skews development to make consistent asymmetrical choices?
In mammals, we’re getting close to the answer. And it looks to be beautifully elegant—it’s a simple trick to convert an anterior-posterior difference into a left-right one.
How do evolutionary novelties arise? The conventional explanation is that the first step is the chance formation of a genetic mutation, which results in a new phenotype, which, if it is favored by selection, may be fixed in a population. No one sensible can seriously argue with this idea—it happens. I’m not going to argue with it at all.
However, there are also additional mechanisms for generating novelties, mechanisms that extend the power of evolutionary biology without contradicting our conventional understanding of it. A paper by A. Richard Palmer in Science describes the evidence for an alternative mode of evolution, genetic assimilation, that can be easily read as a radical, non-Darwinian, and even Lamarckian pattern of evolution (Sennoma at Malice Aforethought has expressed concern about this), but it is nothing of the kind; there is no hocus-pocus, no violation of the Weissmann barrier, no sudden, unexplained leaps of cause-and-effect. Comprehending it only requires a proper appreciation of the importance of environmental influences on development and an understanding that the genome does not constitute a descriptive program of the organism.
This article is part of a series of critiques of Jonathan Wells’ The Politically Incorrect Guide to Darwinism and Intelligent Design that will be appearing at the Panda’s Thumb over the course of the next week or so. Previously, I’d dissected the summary of chapter 3. This is a longer criticism of the whole of the chapter, which is purportedly a critique of evo-devo.
Jonathan Wells is a titular developmental biologist, so you’d expect he’d at least get something right in his chapter on development and evolution in The Politically Incorrect Guide to Darwinism and Intelligent Design, but no: he instead uses his nominal knowledge of a complex field to muddle up the issues and misuse the data to generate a spurious impression of a science that is unaware of basic issues. He ping-pongs back and forth in a remarkably incoherent fashion, but that incoherence is central to his argument: he wants to leave the reader so baffled about the facts of embryology that they’ll throw up their hands and decide development is all wrong.
Do not be misled. The state of Jonathan Wells’ brain is in no way the state of the modern fields of molecular genetics, developmental biology, and evo-devo.
The Friends of Charles Darwin website update I mentioned yesterday is complete (I toasted it with a latte instead of a whiskey, I’m afraid). You do know that if you join, you are then entitled to put an official “FCD” after your name, which looks very distinguished and high-falutin’ (I just refrain because I’m shy about bragging about my honors.) The FCD requires just about as much work and more intelligence than the Ph.D. that Kent Hovind has after his name, so it’s worth going for.
Palaeos is gone! There is a brief note about being unable to support it any longer, and then poof, it’s offline. Martin Brazeau has a comment on it’s value; you can still see fragments of this great resource in google’s cache, but even that will fade too soon.
This is troubling, and it’s one of the worrisome aspects of using the net—there’s no sense of permanence. It would be good if someone were to step forward and at least archive all of the pages, but the essential feature of the Palaeos site was that it was continually maintained and updated to reflect current information, and that’s not something that can be supported without the dedication of much time and effort by someone knowledgeable in the subject.
Next time you’re cutting up a fresh bird, try looking for the lungs. They’re about where you’d expect them to be, but they’re nestled up dorsally against the ribs and vertebrae, and they’re surprisingly small. If you think about it, the the thorax of a bird is a fairly rigid box, with that large sternal keel up front and short ribs—it’s a wonder that they are able to get enough air from those tiny organs with relatively little capability for expanding and contracting the chest.
How they do it is an amazing story. Birds have a radically effective respiratory system that works rather differently than ours, with multiple adaptations working together to improve their ability to take in oxygen. There is also a growing body of evidence that dinosaurs also shared many of these adaptations, tightening their link to birds and also making them potentially even more fierce—they were big, they were active, and their lungs were turbocharged.
Zimmer has a summary of the latest discoveries in the evolution of the baleen whales. It’s beautiful stuff, with the lineage showing their origin from toothed whales, through a phase where they had both teeth and baleen, to their current condition lacking teeth and having only baleen.
I’ve been getting swamped with links to this hot article, “Evolution reversed in mice,” including one from my brother (hi, Mike!). It really is excellent and provocative and interesting work from Tvrdik and Capecchi, but the news slant is simply weird—they didn’t take “a mouse back in time,” nor did they “reverse evolution.” They restored the regulatory state of one of the Hox genes to a condition like that found half a billion years ago, and got a viable mouse; it gives us information about the specializations that occurred in these genes after their duplication early in chordate history. I am rather amused at the photos the news stories are all running of a mutant mouse, as if it has become a primeval creature. It’s two similar genes out of a few tens of thousands, operating in a modern mammal! The ancestral state the authors are studying would have been present in a fish in the Cambrian.
I can see where what they’ve actually accomplished is difficult to explain to a readership that doesn’t even know what the Hox genes are. I’ve written an overview of Hox genes previously, so if you want to bone up real quick, go ahead; otherwise, though, I’ll summarize the basics and tell you what the experiment really did.
