I’m ensconced in a comfy chair at the Bell Museum, waiting for the MnCSE Science Education Saturday meeting to start. I’ll take notes and be sure to put up a summary later today.
It’s not too late to come on down!
Mike Klymkowsky is selling some snazzy evo-wear in the name of bioliteracy. I’m definitely going to have to get that tree of life t-shirt.
Here’s yet another set of Evo-T shirts. No self-respecting biologist need expose his or her breasts to the world ever again!
Fascinating stuff…read this paper in PNAS, Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage, or this short summary, or John Hawks’ excellent explanation of the concepts, it’s all good. It’s strong evidence for selection in human ancestry for a gene, and just to make it especially provocative, it’s all about a gene known to be involved in brain growth, and it’s also showing evidence for interbreeding between Homo sapiens and Neandertal man.
The short short explanation: a population genetics study of a gene called microcephalin shows that a) it arose and spread through human populations starting about 37,000 years ago, b) this particular form of the gene (well, a small cluster of genes in a particular neighborhood) arose approximately 1.1 million years ago in a lineage distinct from that of modern humans, and c) the likeliest explanation for this difference is that that distinct lineage interbred with modern humans 37,000 years ago, passing on this particular gene variant that was then specifically selected for, a process called introgression.
The work looks sound to me, and I’m convinced. The one thing to watch for, though, is that there will be attempts to overreach and couple possession of this gene to some kind of intellectual superiority. We don’t know what this particular variant of the gene does yet! All we can say at this point is that some abstract data shows that a particular allele spread through the human population at a rate greater than chance would predict, that the gene itself has as one of its functions the regulation of brain growth, but that it is highly unlikely that that particular function is affected by the variant. Whatever it does, I expect the role is more along the lines of subtle fine-tuning rather than simply making people smart.
This odd marine worm, Xenoturbella bocki, is in the news right now, and I had to look it up in Pechenik’s Biology of the Invertebrates(amzn/b&n/abe/pwll) to remind myself of what it was. Here’s the complete entry:
Xenoturbella bocki
This marine worm, first described in 1949 as an acoel flatworm and later claimed as either an early metazoan offshoot or a primitive deuterostome, has recently been affiliated with primitive bivalve molluscs, based upon a study of gamete development (oogenesis) and an analysis of sequence data from both 18S rRNA and mitochondrial genes. Little is known about its reproductive mode, and developmental studies that might help to resolve the phylogenetic issues are just starting to be reported. A second species was described in 1999.
The animals are up to 4 cm long, vermiform (worm-shaped), and covered by locomotory cilia. They have no digestive tract, and indeed no organs at all. Their only conspicuous morphological feature, other than their cilia, is a statocyst for determining orientation. To date, they have been collected only off the coasts of Sweden and Scotland, in sediments at depths of 20 m to 100 m.
That’s it. Part of that is now known to be wrong: the data showing an affinity to the molluscs is an artifact, caused by the fact that it somehow eats bivalves, and partly digested clam material contaminated the samples. Otherwise, not much is known; I’ve found papers describing the presence of oocytes inside the animal, but no one as far as I know has actually observed its development. It’s a strange, mysterious blob of a worm.
The life of a parasite must be a good one, and often successful; the creature at the top of the drawing above is a primitive lamprey from the Devonian, 360 million years ago, and the similarities with the modern lamprey (at the bottom) are amazing. It’s less eel-like and more tadpole-like than modern forms, but it has the same disc-shaped mouth specialized for latching on to the flank of its host, it has similar circumoral teeth for rasping through scales and skin for its blood meal, the same pharyngeal adaptations for a life spent clamped to a fish.
I’ve put a photo of the fossil and a cladogram below the fold.
Warren sent me link from The Indigestible, wondering if I was interested in these kinds of speculative questions about the existence of alien life. Why, yes I am…and even wrote something along the same lines a few years ago, coming to the same conclusions: I think intelligent extraterrestrials are unlikely.
My reasons are below the fold. Of course, I will retract my opinion immediately when Klaatu lands.
There is a treasure trove in China: the well-preserved phosphatized embryos of the Doushantuo formation, a sampling of the developmental events in ancient metazoans between 551 and 635 million years ago. These are splendid specimens that give us a peek at some awesomely fragile organisms, and modern technology helps by giving us new tools, like x-ray computed tomography (CT), scanning electron microscopy (SEM), thin-section petrography, synchrotron X-ray tomographic microscopy (SRXTM), and computer-aided visualization, that allow us to dig into the fine detail inside these delicate specimens and display and manipulate the data. A new paper in Science describes a survey of a large collection of these embryos, probed with these new techniques, and rendered for our viewing pleasure…that is, we’ve got pretty pictures!
Here’s another tetrapodomorph fish to consternate the creationists. These Devonian/Carboniferous animals just keep popping up to fill in the gaps in the evolutionary history of the tetrapod transition to the land—the last one was Tiktaalik.
This lovely beastie is more fish than frog, as you can tell—it was a marine fish, 384-380 million years old, from Australia, and it was beautifully preserved. Gogonasus is not a new species, but the extraction and analysis of a new specimen has caused its position in the evolutionary tree to be reevaluated.
Yes! You can now read the complete works of Charles Darwin free, online. Since an original copy of The Origin will set you back roughly $50,000, last I heard, this is a really good deal.
Did the internet get stupider while I was away this past week? I mean, it’s gratifying to my ego to imagine the average IQ of the virtual collective plummeting when I take some time off, but I really can’t believe I personally have this much influence. Maybe the kooks crept out in my absence, or maybe it was just the accumulation of a week’s worth of insanity that I saw in one painful blort when I was catching up.
What triggers such cynicism is the combination of Deepak Chopra, Oliver Curry, and now,
William Tucker. Tucker wrote a remarkably silly piece in the American Spectator in which he drew deeply faulty conclusions from human genetics to support a thesis rife with misogyny and foolish chauvinism on human evolution. It was like a piece on evolutionary psychology written by someone who didn’t know any genetics at all.
Hang on to your hats—we’re going to see a factoid from one magazine article balloon up into a declaration of the superiority of the male species (I use “species” here both ironically and mockingly).
