Lamprey skeletons

Bone is a sophisticated substance, much more than just a rock-like mineral in an interesting shape. It’s a living tissue, invested with cells dedicated to continually remodeling the mineral matrix. That matrix is also an intricate material, threaded with fibers of a protein, type II collagen, that give it a much greater toughness—it’s like fiberglass, a relatively brittle substance given resilience and strength with tough threads woven within it. Bone is also significantly linked to cartilage, both in development and evolution, with earlier forms having a cartilaginous skeleton that is replaced by bone. In us vertebrates, cartilage also contains threads of collagen running through it.

These three elements—collagen, cartilage, and bone—present an interesting evolutionary puzzle. Collagen is common to the matrices of both vertebrate cartilage and bone, yet the most primitive fishes, the jawless lampreys and hagfish, have been reported to lack that particular form of collagen, suggesting that the collagen fibers are a derived innovation in chordate history. New work, though, has shown that there’s a mistaken assumption in there: lampreys do have type II collagen! This discovery clarifies our understanding of the evolution of the chordate skeleton.

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Jurassic beaver

Say hello to Castorocauda lutrasimilis, a primitive mammalioform from the middle Jurassic—164 million years ago. Despite its great age, it has evidence of fur and guard hairs still preserved in the fossil, and was rather large for its time. It’s estimated to have weighed about 500g (about a pound) and was over 400mm (over a foot) long in life, and as you can see from the reconstruction, shows signs of being aquatic. In size and lifestyle, it probably resembled the modern platypus.

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Sensitivity, charm and cleverness: very sexy

Ah, the life of the female giant Australian cuttlefish…males fight for her affections, and during the mating season she will have sex with 2-8 different males each day, with an average total of 17 copulations per day. She can be picky, too, and rejects most of the mating attempts (yet still manages to mate up to 40 times a day). It must be a good life.

Males have a rougher time of it, I would think. There are many more males than females, and so it’s a struggle to get access to one; the bigger, stronger males will guard females, acting as a consort, and use aggressive displays to chase off competitors. What to do if you’re a smaller, but clever male?

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Chicken, archosaur…same difference

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My daughter is learning about evolution in high school right now, and the problem isn’t with the instructor, who is fine, but her peers, who complain that they don’t see the connections. She mentioned specifically yesterday that the teacher had shown a cladogram of the relationships between crocodilians, birds, and mammals, and that a number of students insisted that there was no similarity between a bird and an alligator.

I may have to send this news article to school with her: investigators have found that a mutation in chickens causes them to develop teeth—and the teeth resemble those of the common ancestor of alligators and chickens, an archosaur.

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A better strategy for advancing science

Matthew Nisbet has a good list of things we ought to be doing. Number one on the list is what I also think is the biggest thing we have to do:

SCIENCE EDUCATION REMAINS CENTRALLY IMPORTANT.

And I have to admit that educating you, the readers of this weblog, is actually a small part of the task. The real job lies with our public school teachers—they’re the ones shaping the education of the next generation—and no matter what we do right now, the evolution-creation struggle in the public consciousness is going to be going on for at least the next 20 years. It’s very easy to wreck a school and foster ignorance; it’s very difficult to crawl out of the rubble.

The cephalopod sex series

As part of the ongoing migration to the new site, I’ve brought over some strangely popular articles: Tentacle sex, Tentacle sex, part deux, Squid nuptial dances, and Octopus sex. All across the world, people are wondering what the etiquette is if they should find themselves in a romantic situation with an amorous cephalopod, and it is my duty to provide the answers.

If only I’d thought of bringing these over last week, in time for Valentine’s Day. I hope no one made any beastly gaffes because they couldn’t find these articles in time…

It’s not just the genes, it’s the links between them

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Once upon a time, I was one of those nerds who hung around Radio Shack and played about with LEDs and resistors and capacitors; I know how to solder and I took my first old 8-bit computer apart and put it back together again with “improvements.” In grad school I was in a neuroscience department, so I know about electrodes and ground wires and FETs and amplifiers and stimulators. Here’s something else I know: those generic components in this picture don’t do much on their own. You can work out the electrical properties of each piece, but a radio or computer or stereo is much, much more than a catalog of components or a parts list.

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Electronics geeks know the really fun stuff starts to happen when you assemble those components into circuits. That’s where the significant work lies and where the actual function of the device is generated—take apart your computer, your PDA, your cell phone, your digital camera and you’ll see similar elements everywhere, and the same familiar components you can find in your Mouser catalog. As miniaturization progresses, of course, more and more of that functionality is hidden away in tiny integrated circuits…but peel away the black plastic of those chips, and you again find resistors and transistors and capacitors all strung together in specific arrangements to generate specific functions.

We’re discovering the same thing about genomes.

The various genome projects have basically produced for us a complete parts list—a catalog of bits in our toolbox. That list is incredibly useful, of course, and represents an essential starting point, but how a genome produces an organism is actually a product of the interactions between genes and gene products and the cytoplasm and environment, and what we need next is an understanding of the circuitry: how Gene X expression is connected to Gene Y expression and what the two together do to Gene Z. Some scientists are suggesting that an understanding of the circuitry of the genome is going to explain some significant evolutionary phenomena, such as the Cambrian explosion and the conservation of core genetic processes.

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