Today, Greta Christina has weighed in.
Comments closed here, because I’ve put up with enough of the hysterical delusions of people offended by calm, nuanced, proportionate statements. It’s like the responses to those mild bus signs like “You can be good without god” that leave some people profoundly and irrationally upset. We’ve now found an analog: “guys, don’t do that.”
Take it to Greta’s place if you need to complain.
I’ll be talking with Barry Lynn this afternoon at 3pm ET. I guess it’s live, and you can even call in (866-582-9933) with questions. I wonder what we’ll talk about?
That’s why I’m posting this video.
(Last edition of TET; Current totals: 12,716 entries with 1,433,426 comments.)
That’s not hyperbole. I really mean it. How else could I react when I open up the latest issue of Bioessays, and see this: Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules. Just from the title alone, I’m immediately launched into my happy place: sitting on a rocky beach on the Pacific Northwest coast, enjoying the sea breeze while the my wife serves me a big platter of bacon, and the cannula in my hypothalamus slowly drips a potent cocktail of cocain and ecstasy direct into my pleasure centers…and there’s pie for dessert. It’s like the authors know me and sat down to concoct a title where every word would push my buttons.
The content is pretty good, too. It’s not perfect; the development part is a little thin, consisting mainly of basic comparative embryology of body plans, with nothing at all really about deployment of and interactions between significant developmental genes. But that’s OK. It’s in the nature of the Greatest Science Papers Ever Written that stuff will have to be revised and some will be shown wrong next month, and next year there will be more Greatest Science Papers Ever Written — it’s part of the dynamic. But I’ll let it be known, now that apparently the scientific community is aware of my obsessions and is pandering to them, that the next instantiation needs more developmental epistasis and some in situs.
This paper, though, is a nice summary of the emerging picture of cephalopod evolution, as determined by the disciplines of paleontology, comparative embryology, and molecular phylogenetics, and that summary is internally consistent and is generating a good rough outline of the story. And here is that story, as determined by a combination of fossils, molecular evidence, and comparative anatomy and embryology.
Cephalopods evolved from monoplacophoran-like ancestors in the Cambrian, about 530 million years ago. Monoplacophorans are simple, limpet-like molluscs; they crawl about on the bottom of the ocean under a cap-like shell, foraging snail-like on a muscular foot. The early cephalopods modified this body plan to rise up off the bottom and become more active: the flattened shell elongated to become a cone-like structure, housing chambers for bouyancy. Movement was no longer by creeping, but used muscular contractions through a siphon to propel the animal horizontally. Freed from its locomotor function, the foot expanded into manipulating tentacles.
These early cephalopods, which have shells common in the fossil record, would have spent their lives bobbing vertically in the water column, bouyed by their shells, and with their tentacles dangling downward to capture prey. They wouldn’t have been particularly mobile — that form of a cone hanging vertically in the water isn’t particularly well-streamlined for horizontal motion — so the next big innovation was a rotation of the body axis, swiveling the body axis 90° to turn a cone into a torpedo. There is evidence that many species did this independently.
We can still see vestiges of this rotation in cephalopod embryology. If you look at early embryos of cephalopods (at the bottom of the diagram below), you see the same pattern: they are roughly disc-shaped, with a shell gland on top and a ring of tentacle buds on the bottom. They subsequently extend and elongage along the embryonic dorsal-ventral axis, which becomes the anterior-posterior axis in the adult.
The next division of the cephalopods occurred in the Silurian/Devonian, about 416 million years ago, and it involved those shells. Shells are great armor, and in the cephalopods were also an organ of bouyancy, but they also greatly limit mobility. At that early Devonian boundary, we see the split into the two groups of extant cephalopods. Some retained the armored shells; those are the nautiloids. Others reduced the shell, internalizing it or even getting rid of it altogether; those are the coleoids, the most successful modern group, which includes the squids, cuttlefish, and octopuses. Presumably, one of the driving forces behind the evolution of the coleoids was competition from that other group of big metazoans, the fish.
The nautiloids…well, the nautiloids weren’t so successful, evolutionarily speaking. Only one genus, Nautilus has survived to the modern day, and all the others followed the stem-group cephalopods into extinction.
The coleoids, on the other hand, have done relatively well. The number of species have fluctuated over time, but currently there are about 800 known species, which is respectable. The fish have clearly done better, with about 30,000 extant species, but that could change — there are signs that cephalopods have been thriving a little better recently in an era of global warming and acute overfishing, so we humans may have been giving mobile molluscs a bit of a tentacle up in the long evolutionary competition.
There was another major event in coleoid history. During the Permian, about 276 million years ago, there was a major radiation event, with many new species flourishing. In particular, there was another split: between the Decabrachia, the ten-armed familiar squid, and the Vampyropoda, a group that includes the eight-armed octopus, the cirroctopodes, and Vampyroteuthis infernalis. The Vampyropoda have had another locomotor shift, away from rapid jet-propelled movement to emphasizing their fins for movement, or in the case of the benthic octopus, increasing their flexibility to allow movement through complex environments like the rocky bottom.
Time for the big picture. Here’s the tree of cephalopod evolution, using dates derived from a combination of the available fossil evidence and primarily molecular clocks. The drawings illustrate the shell shape, or in the case of the coleoids, the shape of the internal shell, or gladius, if they have one.
The story and the multiple lines of evidence hang together beautifully to make a robust picture of cephalopod evolution. The authors do mention one exception: Nectocaris. Nectocaris is a Cambrian organism that looks a bit like a two-tentacled, finned squid, which doesn’t fit at all into this view of coleoids evolving relatively late. The authors looked at it carefully, and invest a substantial part of the review discussing this problematic species, and decided on the basis of the morphology of its gut and of the putative siphon that there is simply no way the little beast could be ancestral to any cephalopods: it’s a distantly related lophotrochozoan with some morphological convergence. It’s internal bits simply aren’t oriented in the same way as would fit the cephalopod body plan.
So that’s the state of cephalopod evolution today. I shall be looking forward to the Next Great Paper, and in particular, I want to see more about the molecular biology of tentacles — that’s where the insights about the transition from monoplacophoran to cephalopod will come from, I suspect.
Kröger B, Vinther J, Fuchs D (2011) Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules: Extant cephalopods are younger than previously realised and were under major selection to become agile, shell-less predators. Bioessays doi: 10.1002/bies.201100001.
I’ve never heard of Alex Beam before, which is a good thing — he seems to be some kind of journalist at the Boston Globe, and that’s about all I know about him, other than that he seems to be an oblivious idiot. He has a column up in which he rages about the phrase “knowledge-based”, apparently because he doesn’t understand it. His first target is to fulminate against that expression, “reality based”, which many on the left adopted after the lunacy of the Bush presidency, a phrase invented by the Bushies to describe us:
The aide said that guys like me were “in what we call the reality-based community,” which he defined as people who “believe that solutions emerge from your judicious study of discernible reality.” … “That’s not the way the world really works anymore,” he continued. “We’re an empire now, and when we act, we create our own reality. And while you’re studying that reality–judiciously, as you will–we’ll act again, creating other new realities, which you can study too, and that’s how things will sort out. We’re history’s actors…and you, all of you, will be left to just study what we do.”
Beam doesn’t understand this. His rebuttal registers complete incomprehension.
The Bush presidency always seemed quite fact-freighted to me. The 9/11 attacks were plenty factual, as were the subsequent invasions of Afghanistan and Iraq, and the tens of thousands of deaths that ensued.
Yes. People died on 9/11; that’s real. Even more people died in Afghanistan and Iraq; that’s also real. What Beam glosses over is that there was no credible connection between those two countries and the deaths in New York, and that the Right failed to “create” their own personal, private reality.
A reality-based community would suggest that when you’re attacked, you should respond by evaluating the causes and retaliate appropriately, rather than deciding that here’s a fine time to build an empire. I don’t think that’s so hard to understand.
Then he throws another random example at us.
What in heaven’s name, for instance, is “evidence-based medicine”? Here is a quote from the august British Medical Journal that should set us straight: “Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.” And the opposite of this would be … divination? Are men and women trooping out of the nation’s medical schools trained to flip coins or toss the I Ching on the floor of the intensive care unit if a diagnosis isn’t quickly forthcoming?
Deepak Chopra. Oprah Winfrey. The Center for Spirituality and Healing. Homeopathy. Acupuncture. Reflexology. Iridology. Dr Oz. Anti-vaccination movements. Therapeutic Touch.
Yes, some of them are coming out of our med schools, most are pouring out over the television and radio — we have swarms of men and women peddling non-evidence-based medicine, utter, non-functional, untested, useless garbage at sick people. There clearly are a great many quacks pushing fake remedies that ignore and even contradict the evidence.
Alex Beam must live inside a windowless Faraday cage to be unaware of the realities that are being flouted every day. And he really calls himself a journalist? He does conclude with an ironic comment.
Knowledge-based journalism? Good grief. If that catches on, people like me will be out of a job.
We can always hope.
When I was in London last month, Richard Dawkins and I had a public conversation sponsored by the British Humanist Association, and now you can watch it wherever.
And here’s the Q&A:
They’re just not very bright and don’t know much about them.
Richard Ruelas, a reporter for The Arizona Republic, found himself staring down the barrel of Republican state Sen. Lori Klein’s raspberry-pink firearm during a recent interview at the Capitol.
“Oh, it’s so cute,” Klein said of the .380 Ruger that she carries in purse at all times.
While the loaded pistol had no safety and the laser pointer was centered on the reporter’s chest, Klein explained that there was no need to worry.
“I just didn’t have my hand on the trigger,” she said.
I think there’s good cause to revoke her permit to carry, and for the NRA to come howling down on her in righteous wrath. Not that I imagine for an instant that it will actually happen.
Remember Be Scofield and his bad list of atheist errors? Now Greta Christina takes him on, rather thoroughly.
One of the advantages of being an old geezer is that I remember watching this kind of thing as it was happening, and having to keep the television on all day and all night to catch the latest news from the Moon. You young whippersnappers just get it handed to you at your convenience on this youtube thingie.
It was awesome then, and it’s awesome now.
(via Carl Zimmer)
I hope this is something we can all agree on. Today is the The International Day against Stoning, a consciousness-raising event organized by Mina Ahadi, Patty Debonitas, and Maryam Namazie to call attention to the fact that some countries still practice public stonings as punishments for petty offenses against propriety. There are people in prison right now, awaiting that day when authorities drag them into the public square and people murder them by battering them with rocks.
As you know Sakineh Mohammadi Ashtiani is still languishing in prison. The authorities recently mentioned her case saying that no final decision had yet been reached on her stoning sentence and that Sakineh must remain in prison. Falsely accused of murdering her husband, her only crime is that she is a woman in Iran. Her lawyer, Sajjad Houtan Kian, also remains in prison for having had the courage to defend her and other women with stoning sentences in Tabriz prison; he has been sentenced to four years imprisonment, been put under a lot of pressure and lost 20 kilos (44 pounds) as a result.
The campaign to Save Sakineh Mohammadi Ashtiani has been an important one. It has spoken out in defence of humanity, and against the barbaric punishment of stoning everywhere. It has mobilised immense pressure against and condemnation of the Islamic regime of Iran from millions across the globe. These are accomplishments we must all be proud of.
On 11 July 2011, the International Day against Stoning, let’s once again step up the pressure to demand Sakineh’s immediate release and an end to stoning. Join us by either standing in a city square with a photo or poster of Sakineh, tweeting, or by organising an act of solidarity or a flash mob to raise awareness and attention. On 11 July, in 100 cities worldwide, let us once again raise the banner of humanity against one of the barbarisms of our time.
Follow the link; there are recommendations and addresses for letters of protest. Make it known that the international community regards these barbarous, vile practices as heinous and contemptible.
