I have another short piece commissioned by Forbes magazine in one of their special reports. The section is called “Work Is…”, and there are some provocative ideas in there. My own article is answering the question, “Do Animals Work?” and as you might guess, the answer is yes. I think I got one of the easier topics, actually.
I saw it first at Virge’s place, but Mike Snider is also on the blogroll and I would have gotten to it eventually…but hey, if you’re a fan of fossil tetrapods and poetry, here’s a treat: a Tiktaalik sonnet. You can also view some drafts of its construction, which is developmentally interesting, I think, and not quite as messy as chopping up embryos.
I think my title reveals why I’ll leave the poesy to the pros.
I just learned (via John Lynch) about a paper on cetacean limbs that combines developmental biology and paleontology, and makes a lovely argument about the mechanisms behind the evolution of whale morphology. It is an analysis of the molecular determinants of limb formation in modern dolphins, coupled to a comparison of fossil whale limbs, and a reasonable inference about the pattern of change that was responsible for their evolution.
One important point I’d like to make is that even though what we see in the morphology is a pattern of loss—whale hindlimbs show a historical progression over tens of millions of years of steady loss, followed by a near-complete disappearance—the molecular story is very different. The main players in limb formation, the genes Sonic hedgehog (Shh), the Fgfs, and the transcription factor Hand2, are all still present and fully functional in these animals. What has happened, though, is that there have been novel changes to their regulation. Even loss of structures is a consequence of changes and additions to regulatory pathways.
Chad reports a not-so-subtle message from a science conference:
The annoying thing was the peripheral message– she took pains to state several times that both Democrats and Republicans in Congress support science, in a tone that basically came across as chiding us for thinking otherwise. That was annoying by itself, but at the very end of the talk, she specifically warned against taking partisan positions, citing the letter supporting John Kerry that was signed by a couple dozen Nobel laureates as something that made it harder to keep science funding. She said that after that, when she met with administration officials about budget matters, she could see them thinking “Damn scientists…”
When the government says or does something scientifically stupid, it is our solemn duty to go along with it.
I’m going to briefly summarize an interesting new article on cnidarian Hox genes…unfortunately, it requires a bit of background to put it in context, so bear with me for a moment.
First you need to understand what Hox genes are. They are transcription factors that use a particular DNA binding motif (called a homeobox), and they are found in clusters and expressed colinearly. What that means is that you find the Hox genes that are essential for specifying positional information along the length of the body in a group on a chromosome, and they are organized in order on the chromosome in the same order that they are turned on from front to back along the body axis. Hox genes are not the only genes that are important in this process, of course; animals also use another class of regulatory genes, the Wnt genes, to regulate development, for instance.
A gene can only be called a Hox gene sensu stricto if it has a homeobox sequence, is homologous to other known Hox genes, and is organized in a colinear cluster. If such a gene is not in a cluster, it is demoted and called simply a Hox-like gene.
Hox genes originated early in animal evolution. Genes containing a homeobox are older still, and are found in plants and animals, but the particular genes of the Hox system are unique to multicellular animals, and that key organization arrangement of the set of Hox genes in a cluster is more unique still. The question is exactly when the clusters arose, shortly after or sometime before the diversification of animals.
If you take a look at animal phylogeny, an important group are the diploblastic phyla, the cnidarians and ctenophores. They branched off early from the metazoan lineage, and they possess some sophisticated patterns of differentiation along the body axis. We know they have homeobox containing genes that are related to the ones used in patterning the bodies of us vertebrates, but are they organized in the same way? Did the cnidaria have Hox clusters, suggesting that the clustered Hox genes were a very early event in evolution, or do they lack them and therefore evolved an independent set of mechanisms for specifying positional information along the body axis?
Four of my favorite things are development, evolution, and breasts, and now I have an article that ties them all together in one pretty package. It’s a speculative story at this point, but the weight of the evidence marshaled in support of the premise is impressive: the mammalian breast first evolved as an immunoprotective gland that produced bacteriocidal secretions to protect the skin and secondarily eggs and infants, and that lactation is a highly derived kind of inflammation response. That mammary glands may have had their origin as inflamed glands suppurating mucus may not be the most romantic image to arise in a scientific study, but really—they got better and better over the years.
Human milk is potent stuff. The Greek for milk was gala, and as you might be able to see if I hadn’t had to reduce this Tintoretto so much, the galaxies were created from the spray of milk from Hera’s breasts. Modern astronomers might quibble with that explanation of the origins of the extrasolar universe, but what do I know…I’m a biologist. I’ll stick to biology now, and with that, here’s a short summary of the biology behind mother’s milk.
I’m going to link to a post on Uncommon Descent. I try to avoid that, because I think it is a vile harbor of malign idiocy, but Dembski has just put up something that I think is merely sincerely ignorant. That’s worth correcting. It also highlights the deficiencies of Dembski’s understanding of biology.
Dembski makes a strange argument for ID on the basis of a certain class of experiments in developmental biology.
Whoa, it’s been a while since I’ve said anything about my infatuation with cephalopods (since, like, the last post…). Let’s correct that with a nifty paper I found on octopus suckers.
Here’s a typical view of a tangle of octopus arms, all covered with circular suckers. The octopus can cling to things, grasp prey and other objects with those nifty little discs, and just generally populate people’s nightmares with the idea of all those grappling, clutching, leech-like appendages.
Seed has started this thing they’re calling “Ask a Science Blogger,” in which we’re supposed to take provocative questions and answer them here. You know, like those ice-breaking party games, supposed to get the social bonding thing going, foster unity, etc. Only thing is, they don’t quite get the idea yet—they’re asking the science bloggers to come up with questions to ask the science bloggers. “What’s that?” I say, “why not cut out the middleman and not ask the questions that nobody’s asking that we’re being asked to answer? Saves time.”
That’s too mean-spirited, so let’s turn it around in true weblogging fashion and ask you, the loyal readers, to invent the questions that we’ll ask the bloggers that they might then answer. These will then get passed up the corporate food chain, filtered and processed, and come back down to us in a little game of telephone. You know, you’ll ask some great question like “How does a pycnogonid eat an opisthobranch?” and the question of the week will be “How do pygmies greet the opposite rank?” and we’ll all sit here baffled. It will be great Science.
To prime the pump, here are a few questions that I thought would be fun.
I’m sure you can come up with much better ones. If you don’t feel like asking questions, there’s nothing stopping you from answering them!
