evolution
loom | February 27, 2006This image came out a couple months ago in Nature, but I just came across it today. I quite like the way it sums up the history of life--something that's maddening hard to do, since the time scales are so vast. It shows how life's diversity has been accumulating for billions of years. This chart shows the timing of the earliest paeolontological evidence for different kinds of life, ranging from fossils to chemical markers. A few definitions may help. Phototrophic bacteria can harness sunlight to grow. Cyanobacteria are also known as blue-green algae (aka pond scum). Eukaryotes are species…
pharyngula | February 27, 2006Bone 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…
stcynic | February 27, 2006Mark Creech, the head of a group called the Christian Action League of North Carolina, has a pretty typical creationist response to the Clergy Letter Project. In the process, he manages to completely mangle how science operates and misrepresent the relationship between observation and proof. And of course, he trots out a couple of tried and true out of context quotes along the way. What would a creationist tract be without them?
It is most unfortunate so many Christian leaders have concluded that evolution is scientific, whereas creationism and intelligent design are simply religious -- when…
evolgen | February 25, 2006I have always been disappointed by the EvoWiki -- I found that I could get better information on evolutionary biology from the regular Wikipedia. Now some folks have organized the evolution content on Wikipedia into navigation templates. I have not examined the content of the entries listed in these templates, but this seems like a cool idea.
Evolution: http://en.wikipedia.org/wiki/Template:Evolution
Population genetics: http://en.wikipedia.org/wiki/Template:Popgen
Development of phenotype (or "genetic architecture", its original name): http://en.wikipedia.org/wiki/Template:Genarch…
evolgen | February 24, 2006My apologies for the utter lack of posting over the past week. I've got stuff sitting around waiting to be written about, and I just haven't been writing. I'm not going to make excuses; I just haven't been managing my time well. While you wait for me to post again (soon, I promise), I give you this article on "intelligently designing" promiscuous enzymes to perform specific functions. Here's a quote from the write up:
According to the theory of divergent molecular evolution, primordial enzymes and other proteins started out as "promiscuous" so that primitive organisms would be better able…
pharyngula | February 23, 2006This week's issue of Science contains a very strongly worded statement about the utility of evolutionary biology in medicine, and calls for an increase in education about evolution at all levels of the medical curriculum, from high school to med school. I've put the whole thing below the fold—it's good reading.
Medicine Needs Evolution
The citation of "Evolution in Action" as Science's 2005 breakthrough of the year confirms that evolution is the vibrant foundation for all biology. Its contributions to understanding
infectious disease and genetics are widely recognized, but its full potential…
pharyngula | February 23, 2006Say 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.
Holotype of Castorocauda lutrasimilis [Jinzhou Museum of Paleontology (JZMP) 04-117]. (A) Photograph of the…
cmooney | February 23, 2006PZ and Jason Rosenhouse are blogging about this testy email exchange between two of evolution's top defenders, Michael Ruse and Daniel Dennett. I don't fully grasp how or why these emails got out--it doesn't seem like something that should have happened (although frankly, they're not actually all that salacious anyway). But I would like to wade through a few of the issues they raise.
PZ and Rosenhouse have an interesting reaction to one argument by Michael Ruse that I find fairly persuasive (although it's stated rather hyperbolically here): that Dennett and Richard Dawkins are "absolute…
cmooney | February 23, 2006A new documentary, Flock of Dodos, is now out. The auteur, Randy Olson, is an "evolutionary ecologist with a Ph.D. from Harvard University." But he's also from Kansas originally, and he has made a film that apparently heaps a fair amount of scorn on both sides of the evolution debate:
"Flock of Dodos" audiences laugh at the expense of Olson's own evolutionist friends. While the evolutionists are playing poker and calling intelligent design proponents "yahoos" and "idiots," he turns the evolutionists into animated dodos, the extinct, flightless birds that were known for their lack of grace.
Or…
razib | February 22, 2006The "standard model" of intellectual history presents the Presocratics as the pioneers of naturalistic explanations of the universe around us. This narrative explains how the messy natural philosophy of the Presocratics gave way to the more metaphysical and ethical schools of the late Classical and Hellenistic and Roman eras. In any case, Socialist Swine asks below:
I know that prior to Darwin people had some notion of evolution though they didn't have a notion of the mechanism involved. Do you have any idea, who might have first suggested that species change over time?
Well, 10 minutes…
loom | February 22, 2006Go back far enough in our history--maybe about 650 million years--and you come to a time when our ancestors were still invertebrates. That is, they had no skulls, teeth, or other bones. They didn't even have a brain.
How invertebrates became vertebrates is a fascinating question, made all the more fascinating because the answer tells us something about how we got to be the way we are. In order to reconstruct what happened, scientists can study several different kinds of evidence. They can look at the bodies of invertebrates to find the ones that share traits with vertebrates not found in…
pharyngula | February 22, 2006
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…
razib | February 21, 2006A story in The Economist, titled the fertility bust (in the "Charlemagne" column), offers this interesting tidbit:
Germany is something of an oddity in this. In most countries with low fertility, young women have their first child late, and stop at one. In Germany, women with children often have two or three. But many have none at all.
In other words, the mean for Germany is low, but reproductive variance (or skew) is high. With a large proportion of the population not reproducing, and another proportion reproducing above replacement, this is basically very close to truncation selection if…
oracknows | February 21, 2006His Noodliness walks (or flies) among us, and here's the evidence.
Hey, it's better than any "evidence" that I've seen supporting the existence of UFO's or ghosts.
pharyngula | February 21, 2006Olduvai George shows how to illustrate evolution , with pictures of Eusthenopteron, Pachyaena, and a thylacine.
loom | February 20, 2006In tomorrow's New York Times, I have an article about how new species evolve. It describes new research into how a population can split into two species. The idea that species can evolve when populations get geographically isolated is well-supported by evidence, but the idea that individuals living side by side can split apart (called sympatric speciation) has sparked more controversy. The late biologist Ernst Mayr was the lead champion of the geographic isolation mechanism, and he was always skeptical of claims of sympatric speciation. But, as he said in this 2001 interview, he was…
grrlscientist | February 20, 2006Even though Michael Ruse is an evolutionary philosopher, he also is a self-described deist, so I probably should have been ready to be disappointed. Instead of saving my hard-earned money, I optimistically purchased his book, The Evolution-Creation Struggle (2005, Harvard University Press), with the expectation that it would explain the history that underlies the conflict between science and religion regarding the origins of life on earth, particularly as it is being acted out in science classrooms in America -- which it did accomplish. Kinda. Sorta.
In this book, Ruse defines and explores…
loom | February 20, 2006You and an oak tree have something in common: you're both big. Unlike viruses and bacteria, you and an oak tree are both made up of trillions of cells. There's something else you and an oak tree have in common: you both began as an individual cell, which then divided again and again, its daughter cells differentiating along the way to produce tissues. In your case, they turned into bone, muscle, liver, and such. In the oak's case, the cells became bark, leaf, root.
You and an oak tree have a third thing in common: you evolved from single-celled ancestors. By analyzing DNA from a wide range of…
pharyngula | February 18, 2006
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…