I must be some kind of purist

Lots of sources are telling me about Pat Robertson’s sudden acceptance of the fact of global warming. I’m sorry, but it’s no cause for rejoicing. He accepts it for the wrong reasons.

This week the heat index, the perceived temperature based on both air temperatures and humidity, reached 115 Fahrenheit in some regions of the U.S. East Coast. The 76-year-old Robertson told viewers that was “the most convincing evidence I’ve seen on global warming in a long time.”

If there’s one broad, overall message I wish everyone would get from this blog and from my teaching, it’s that science isn’t about getting the right answers—it’s about how you arrive at your answers, by verifiable, testable, repeatable methods and logic and good evidence. Deciding that global warming occurs because you’re having a hot, sticky, uncomfortable summer: bad and unscientific. Deciding that global warming occurs because the climate research community has evaluated multiple lines of evidence and documented an anomalous pattern: smart.

I’m sorry, Jake, but while getting the religious right on the side of conservation is a good thing, doing so on the say-so of an incompetent authority like Pat Robertson who uses an anecdote about the weather to justify it is a bad thing. What are we going to do if Colorado has a blizzard in January, and James Dobson uses that to argue that an Ice Age is on the way? Or if Jerry Falwell has a bout of incontinence, so he prophesies great floods?

Evolution of median fins

Often, as I’ve looked at my embryonic zebrafish, I’ve noticed their prominent median fins. You can see them in this image, although it really doesn’t do them justice—they’re thin, membranous folds that make the tail paddle-shaped.

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These midline fins are everywhere in fish—lampreys have them, sharks have them, teleosts have them, and we’ve got traces of them in the fossil record. Midline fins are more common and more primitive, yet usually its the paired fins, the pelvic and pectoral fins, that get all the attention, because they are cousins to our paired limbs…and of course, we completely lack any midline fins. A story is beginning to emerge, though, that shows that midline fin development and evolution is a wonderful example of a general principle: modularity and the reuse of hierarchies of genes.

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Voices of science

If you’re at work, I hope you have headphones; if you don’t, check in once you get home. Here are a couple of audio recordings of good science.

Why are flounder funny looking?

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The other day, I was asked a simple question that I knew the answer to, right off the top of my head, and since I’m nothing but lazy and lovin’ the easy stuff, I thought I’d expand on it a bit here. The question was, “How do flounder get to be that way, with their eyes all on one side of the head?” And the answer is…pedantic and longwinded, but not too difficult.

The Pleuronectiformes, or flatfish, are a successful teleost order with about 500 known species, some of which are important commercially and are very tasty. The key to their success is their asymmetry: adults are camouflaged ambush predators who lurk on the sea bottom, taking advantage of their flat shape to rest cryptically and snap up small organisms that wander nearby. They lie on their sides, and have peculiarly lop-sided heads in which one eye has drifted to the other side, so both eyes are peering out from either the left or right side (which side is consistent and characteristic for a particular species, although there is at least one species with random assignment of handedness to individuals, and mutant strains are known in others that reverse the handedness.)

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Ancient rules for Bilaterian development

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Assuming that none of my readers are perfectly spherical, you all possess notable asymmetries—your top half is different from your bottom half, and your front or ventral half is different from you back or dorsal half. You left and right halves are probably superficially somewhat similar, but internally your organs are arranged in lopsided ways. Even so, the asymmetries are relatively specific: you aren’t quite like that Volvox to the right, a ball of cells with specializations scattered randomly within. People predictably have heads on top, eyes in front, arms and legs in useful locations. This is a key feature of development, one so familiar that we take it for granted.

I’d go so far as to suggest that one of the most important events in our evolutionary history was the basic one of taking a symmetrical ball of cells and imposing on it a coordinate system, creating positional information that allowed cells to have specific identities in particular places in the embryo. When the first multicellular colony of identical cells set aside a particular patch of cells to carry out a particular function, say putting one small subset in charge of reproduction, that asymmetry became an anchor point for establishing polarity. If cells could then determine how far away they were from that primitive gonad, evolution could start shaping function by position—maybe cells far away from the gonad could be dedicated to feeding, cells in between to transport, etc., and a specialized multicellular organism could emerge. Those patterns are determined by interactions between genes, and we can try to unravel the evolutionary history of asymmetry with comparative studies of regulatory molecules in early development.

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