I got this email from Alan Kazlev, one of the main fellows working on the Palaeos website (a very useful paleontological resource), which I had previously reported as going offline. Plans are afoot to bring it back, and the answer seems to be to wikify it and build it anew, with a more distributed set of contributors. How Web 2.0! I’ve included the full email below the fold if you’d like more details.
I was reading a review paper that was frustrating because I wanted to know more—it’s on the evolution of complex brains, and briefly summarizes some of the current confusion about what, exactly, is involved in building a brain with complex problem solving ability. It’s not as simple as “size matters”—we have to jigger the formulae a fair bit to take into account brain:body size ratios, for instance, to get humans to come out on top, and maybe bulk is an inaccurate proxy for more significant matters, such as the number of synapses and nerve conduction velocities.
There’s also a growing amount of literature that takes genomic approaches, searching for sequences that show the signatures of selection, and plucking those out for analysis. There have been some provocative results from that kind of work, finding some candidate genes like ASPM, but another of the lessons of that kind of work seems to be that evolution has been working harder on our testis-specific genes than on our brains.
The encouraging part of the paper is that the authors advocate expanding our search for the correlates of intelligence with another group of organisms with a reputation for big brains, but brains that have evolved independently of vertebrates’. You know what I’m talking about: cephalopods!
The Cephalopoda are an ancient group of mollusks originating in the late Cambrian. Ancestors of modern coleoid cephalopods (octopus and squid) diverged from the externally-shelled nautiloids in the Ordovician, with approximately 600 million years of separate evolution between the cephalopod and the vertebrate lineages. The evolution of modern coleoids has been strongly influenced by competition and predatory pressures from fish, to a degree that the behavior of squid and octopus are more akin to that of fast-moving aquatic vertebrates than to other mollusks. Squid and octopuses are agile and active animals with sophisticated sensory and motor capabilities. Their central nervous systems are much larger than those of other mollusks, with the main ganglia fused into a brain that surrounds the esophagus with additional lateral optic lobes. The number of neurons in an adult cephalopod brain can reach 200 million, approximately four orders of magnitude higher than the 20-30,000 neurons found in model mollusks such as Aplysia or Lymnaea. Cephalopods exhibit sophisticated behaviors a number of studies have presented evidence for diverse modes of learning and memory in Octopus and cuttlefish models. This learning capacity is reflected in a sophisticated circuitry of neural networks in the cephalopod nervous system. Moreover, electrophysiological studies have revealed vertebrate-like properties in the cephalopod brain, such as compound field potentials and long-term potentiation. Thus cephalopods exhibit all the attributes of complex nervous systems on the anatomical, cellular, functional and behavioral levels.
Unfortunately, the purpose of the paper is to highlight an unfortunate deficiency in our modern research program: there is no cephalopod genome project. The closest thing to it is an effort to sequence the genome of another mollusc, Aplysia, which is a very good thing—Aplysia is a famous and indispensable subject of much research in learning and memory—but it’s no squid. The authors are advocating additional work on another animal, one with a more elaborate brain.
A parallel effort on a well-studied octopus or squid should provide insights on the evolutionary processes that allowed development of the sophisticated cephalopod nervous system. For example, have cephalopods undergone accelerated evolution in specific nervous system genes, as has been suggested for primates? Have specific gene families undergone expansion in the cephalopod lineage and are these expressed in the nervous system? Are there clear parallels in accelerated evolution, gene family expansion, and other evolutionary processes between cephalopods and vertebrates? Answers to these and related questions will provide useful perspectives for evaluation of the processes thought to be involved in the evolution of the vertebrate brain.
I’m all for it—let’s see a Euprymna genome project!
Jaaro H, Fainzilber M (2006) Building complex brains—missing pieces in an evolutionary puzzle. Brain Behav Evol 68(3):191-195.
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.
