Watson/Wilson

There is good cause to be aggravated by some of James Watson’s recently expressed views, but he’s still an interesting fellow who made a significant contribution to our understanding of biology; and E.O. Wilson, of course, is always cool. So here they are together in an interview with Charlie Rose, discussing the significance of Charles Darwin:

(It was a little too gushy at the beginning — Darwin certainly did get some things very wrong! — but it’s still the kind of conversation it’s fun to hear.)

Anthropology of war

Last weekend’s bloggingheads was an interesting discussion between John Horgan and Brian Ferguson on the unfortunate misconception many people have about human evolution — the simplistic idea that evolution is always about selection for individuals who are better at killing their competitors. It doesn’t work that way! Ferguson discusses the interesting and obvious idea that the data does not back up the notion that being a great warrior is generally a good strategy, because being a great warrior also greatly increases the likelihood that you’ll end up dead.

Evolution is about whatever works, and often cooperation is a winning tactic.

We don’t need teleology — so why bother?

Tony Sidaway discusses a unifying property of theistic evolutionists: the desire or need for there to be some kind of universal plan for their existence. It’s not an attitude I understand very well; I don’t think it makes life better to believe that there is some ineffable teleological intent behind the events in your life, and no one ever bothers to explain why it would be preferable to be a pawn to a cosmic puppetmaster. Their reasoning also tends to be incredibly bad, as can be seen in the article by Mark Vernon that inspired Tony’s musings.

The work of Conway Morris, and now many others, is showing that evolution keeps coming up with the same solutions to natural problems. One of the better-known examples is that sabre-toothed cats. They evolved on at least three different occasions along independent Darwinian paths. And yet they look almost exactly the same. Dozens of examples of convergence have now been documented across a wide variety of biological phenomena, from animal and plant physiology to molecular biology.

Convergence raises the possibility of directionality in evolution. This is anathema to the old school. Strictly speaking, even to talk of adaptations being advantageous is to risk a false sense of teleology. The sense of “advantage” only comes because we have hindsight. As Stephen Jay Gould put it: according to this interpretation of evolution, if you re-ran the “tape of life”, life would look very different.

Convergence challenges this, because in a way, evolution has already re-run the tape of life several times, and it looks strikingly similar.

The argument from convergence is wrong and makes no sense, yet somehow it appeals to smart people like Simon Conway Morris and Ken Miller, who have both made it themes in their books. Convergence occurs, of course, but “dozens of examples” is not very impressive and does not imply that this is a dominant mode of evolution. The examples also exhibit the constraints of contingency; yes, several mammals have evolved saber teeth, which seem to be tools for a particular kind of predation that involves deep tearing to induce bleeding in prey. If we get away from mammals, though, it doesn’t appear very often, if at all. Raptors, for instance, probably used an overdeveloped claw in the same way. Convergence is often a consequence of limitations in anatomy and physiology that make a narrower range of solutions to common problems available.

Another good example is the eye. Eyes have independently evolved multiple times, and we do see examples of convergence — molluscs and vertebrates have simple camera eyes that are not related by ancestry. It’s not because of some master plan, however, but because using a lens to focus light on a sheet of photoreceptive cells is a simple, easily evolved strategy for putting an image on a neuronal array. This is a case where physics itself imposes some limitations on how a receptor organ can function. At the same time, though, life explores a wider set of solutions than we can imagine. Mollusc and vertebrate eyes differ in all the details of their development and anatomy, and obviously enough, other organisms, such as arthropods, have put together radically different solutions with compound eyes. Did a god have a plan that involved eyes forming as orbs with single lenses? Why? And does that make dragonflies satanic, for defying the plan?

Vernon is also completely wrong. The tape of life has not been replayed, except in a small scale and with historical limitations. You could argue, I suppose, that the Permian and Cretaceous extinctions represented a catastrophic rewinding of life’s tape for large terrestrial animals, but do note that each produced different solutions. Dinosaurs became ascendant (in a megafauna sense) after the Permian, but very different vertebrates took over after the Cretaceous.

It’s all very peculiar. This particular breed of teleologist seizes upon small functional similarities in organisms, tooth size or body shape or color pattern, and declares that because two species independently generate similar solutions to common problems, it must be because there is a guiding force producing these solutions. They want the guiding force to be a deity, but unfortunately, Darwin long ago identified the force as short-term local adaptation to environmental forces, nothing more, no grand planner, no deep purpose, and these instances of convergence provide no evidence otherwise.

There must be some psychological need in the teleologists that I lack. I don’t feel any a priori requirement that complexity and adaptation and similar solutions must be driven by any kind of master blueprint, and I find any kind of deterministic explanation for earth’s history to be personally horrifying (not that that is an obstacle to such explanations being true, but it does confuse me that some people think such an answer to be desirable).

We are each our own individual engines of purpose, operating in a hostile universe where randomness can shape our fates. There is no grand scheme behind our existence, other than the same function that all our ancestors had: to order our local environment to allow each to survive and to make the world a little better for our progeny. And that’s enough — that’s all that is needed to make a rich, diverse, living planet, and it’s all I need to live a satisfying life.

PZ’s Galápagos Adventure

Here follows a brief account of my sojourn in the Galápagos Islands, just to give you all a rough idea of what I was up to all this time. I’ve tossed in just a few pictures to illustrate what we experienced; I’m planning to dole out the rest a little bit at a time, each week. I took a lot of pictures, and I was a real piker compared to a few other people on the trip — I’m thinking that if I use mine and some of the other photographs people took, if I post one a week, I’ll be able to keep the blog going for about 3800 years.

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Fragments of a shipboard talk

Since it has been a long time since I contributed any content to Pharyngula…here’s something. I was asked to give a brief talk on the ship, so I’ve tossed my written draft below the fold. With these short talks I like to write the story first, but when I get up on the stage and actually perform it, I don’t bring notes or anything like that, so what is actually said follows the structure of what I wrote, and some of the wording comes through, but it tends to be rather different. Probably a lot different —I know I extemporized a fair bit on the last half. This is all you get until I’ve had a good night’s sleep, though.

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Looking for the lizard guts story?

Another bit of distortion from Ray Comfort: he claims now that I was asked to present the very best evidence for evolution, and that all I could come up with was some “little infolding of the gut”. If you’ve come here from Comfort’s ignorance zone, here are the details of the evolution of lizards of the genus Podarcis.

What Comfort cannot comprehend is that there is no one absolute make-or-break piece of evidence for evolution — evolution is a conclusion from the totality of the evidence. There are thousands of cases that demonstrate that the principles of evolution work and are useful for understanding the natural world; there are no cases where creationism has improved our understanding.

Evolve: Guts

Last week, we watched Evolve: Eyes on the History Channel; tonight, shall we watch the next episode, Evolve: Guts, together? Tune in shortly!

A disgusting beginning: competitive eaters? Bleh. It’s a basic introduction to mammalian digestive physiology — I can tell we’re going to get lots of Big Vertebrate biology again.

They show a cool machine called Cloaca that simulates human digestion, with vats containing chemicals to act as the various chambers. They don’t bother to explain why this machine was built, but it is kind of weirdly interesting.

Once again, they openly say that the complexity of the digestive system evolved — that’s rather refreshing.

Yay! They go back to microorganisms 700 million years ago…for 30 seconds. Then we move on to Ediacaran organisms. The evidence shows that they weren’t photosynthetic, but were some kind of animal that had to have fed somehow, and probably were passive absorbers of drifting nutrients. They suggest that they were replaced by Cambrian organisms that had guts.

Jellyfish just have a sac, not a tube. Cambrian creatures had a more elaborate feeding system, allowing for sophisticated mobile predators, and we see an arms race. Nice animations of Anomalocaris all over the place!

Zip to the modern day: submersibles discover exotic deep sea worms that live on dead whale bones. They have no mouth or gut, so how do they eat bone? They were drilling in and bringing bacteria with them that broke down the bone, and then the worms absorbed the bacteria.

Hey, they mention bacteria, and talk about how digestive enzymes secreted by bacteria are predecessors, and are necessary for the extraction of food in our own guts.

They also mention fish and specialization of regions in the gut tube! More fish, please! But no, we’re going to go straight to tetrapods now, and the promise before the break is dinosaurs. Oh, well.

I’m really pining for more about the actual evolution of guts — and something about development. How can they talk about epithelial tubes without talking about development? Jumping to dinosaurs skips all the interesting stuff. Guts are done by the time you’ve got dinosaurs.

OK, dinosaurs. Yeah, yeah. They discuss gizzard stones and the relationship of dinosaurs to birds. Were dinosaurs warm-blooded? Their digestion was less croc-like and more bird like, determined by analyzing dinosaur coprolites, including T. rex droppings, which contain fragments of fossilized bone. They contain large quantities of bone, which suggests a croc-like eating pattern. But they also contains fragments of fossilized muscle tissue, which suggests that food passed through rapidly, like a bird. So it was a glutton that also had to eat frequently.

The K/T event meant that these big consumers all starved to death. The lead-in to the next section is all about snakes and mammals.

Snakes! Theyre going to talk about the evolution of feeding strategies (why not use cichlids, though? They’d be better). Oh…because you can show movies of snakes swallowing mice whole.

Nifty x-rays of poor mice dissolving in a snake’s gut.

Discussion of the ability of the snake to shut down its gut between meals. Microvilli lining the intestine actually contract while fasting, and increase in length when feeding.

20 million years ago, there was a widespread increase in grasslands that represented a new opportunity … but was hard to eat because much of it was bound up in cellulose. Ruminants evolved fermentation chambers. They show a surgically fistulated cow that allows researchers to get their hands right into a gut. They use bacteria to help break down tough plant material.

These adaptations promote the growth of herbivores…which leads to the evolution of predators.

Now it’s on to humans, of course. They suggest that maybe the key innovation in our ancestors wasn’t our brain, but guts: big-toothed, small-brained apes evolved into small-toothed, big-brained humans. A switch in diet to more meat, and the use of tools to ‘pre-digest’ food allowed us to have smaller guts. Cooking was another huge change that greatly improved the quality of the diet.

They measure the energy required by snakes to digest raw vs. cooked meat. Cooking reduces the cost of digestion by 12.5%. Human guts evolved to be more efficient, liberating more energy for the evolution of the brain.

OK, much like last week’s episode, this show’s strengths are also its weaknesses. The emphasis on charismatic megafauna may be great for catching the attention of casual viewers, but it leaves out all the important events in the evolution of these structures, and ends up emphasizing late refinements and details. Somehow, we need to get a documentary that brings up more molecules and development and the all-important teeny-tiny creatures, where the major innovations first appeared.

But still, I’m most impressed to see a television show that unapologetically discusses evolution as the only credible explanation for the appearance of these features.

TV reminder

Tonight, at 9 Central/10 Eastern, it’s time for the second episode in the History Channel’s series on evolution: Evolve – Guts.

It doesn’t just take willpower to survive. It takes guts–in the form of a digestive system that turns food into fuel. Look closely at the role guts have played in shaping some of Earth’s most successful animals: tyrannosaurs, snakes, cows, humans and others. Take a 575-million year journey that begins with the planet’s first multi-cellular organisms and ends at our dinner tables. Watch as live-action natural history sequences, CGI, epic docudrama, and experimental science help to illustrate our and our fellow species’ eternal struggle for survival on earth.

I think I’d rather hear more about the digestive systems of protists, Trichoplax, sponges, and cnidarians than T. rex again, but shall we watch it together as we did last week?