Dr. Michael J. Ryan's Darwin Day talk

Dr. Michael J. Ryan from University of Texas was one of the speakers who gave a talk at the CFI Darwin Day celebration. It was "Sexual Selection, Darwin's Second Great Theory: Why males are dying to mate". A provocative title, somewhat -- and indeed, the idea of sexual selection was thought to be provocative and radical in Darwin's times. To me it was those historical footnotes that made up the main interest of his speech, as the idea itself wasn't new to me.

Sexual selection theory says animals evolve certain traits not because they help them to survive, but because those traits help them to attract mates -- even when doing so runs counter to survival. This helps explain why in some species males and females are so markedly different in their appearance and behavior. This is evident even in humans, if we believe "men are from Mars, women are from Venus" brand of stereotypes. :-) Behavioral differences between men and women sometimes seem so dramatic, they can make you wonder if men and women are from different planets. In the animal realm one of the most striking examples of appearance differences between sexes is a peacock's tail. That tail is what got Darwin thinking that natural selection in itself was not enough to explain how it evolved. How is it that this trait allowed peacocks to survive better? Darwin decided he needed another theory. So he came up with the sexual selection theory.

Often the traits that help males attract mates are also the ones that makes them more likely to die. Such is the case with tungara frogs, which Dr. Ryan has studied at length. The males of this species are more likely to attract females if their calls are more complex. (Here Dr. Ryan amused the audience by imitating tungara frog calls. He had to do it because sound wasn't working in his presentation. This was just as well, because, according to him, he can make frog calls so realistic he can even trick the frogs into conversing with him. Apparently male tungara frogs view conversation as a competitive sport: they respond with calls that are more complex than the ones they hear.)

However, tungara frogs predators, such as bats, also favor males that make more complex calls. So the individuals that are more attractive to females are also more likely to die. Both selection and counter-selection forces play a role in evolution.

Back in Darwin's time people had hard time accepting the notion that sexual selection is driven by females choosing males with particular characteristics. They said, we only need to reflect on human species to realize how ridiculous this idea is. In Darwin's Victorian England women had very little choice in most things. So Darwin's idea at that time was radical.

Dr. Ryan (who, by the way, considers himself a feminist) noted that even these days there's large feminist literature that absolutely rejects the notion that female choice of mates is the driving force of sexual selection (among animals, at least). They are incredibly critical of this idea.

Pictures from Darwin Day can be found in my photo gallery. I will keep adding new pictures in the days to come.

Darwin Day lectures: Zachary Moore, "Evolution: A Theory Confirmed"

Center For Inquiry celebrated Charles Darwin's 200th birthday on February 15 (3 days after his actual birthday, but we had to wait for the weekend) with a day full of educational activities for children, lectures for grownups, and a dinner. There were three hour-long lectures of evolution. That's a lot to sit through in one chunk of time, but the talks were lively enough to hold my attention. Here's the summary of the first talk, given by Dr. Zachary Moore, a molecular biologist, and titled "Evolution: A Theory Confirmed". It doesn't say anything you wouldn't find elsewhere on the web in more detail, but it briefly sums up the ways evolution science has progressed since Darwin's times.

There were many things that Charles Darwin didn't know about evolution. They were discovered by scientists in the centuries to come. Three kinds of evidence for evolution that were discovered after Darwin's times are:

• speciation in action
• key transitional species
• molecular biology evidence

An example of speciation in action is so-called ring species.

When territories of two different, but related species of animals partially overlap, they can often interbreed. So you have a chain of several species, and any two neighboring species can interbreed between themselves. In a way it's like a spectrum: on one end there is "red" species, which then morphs into orange, yellow, green, and blue. Any color (or at least, individuals on the ends of any color) can interbreed with neighboring colors. But if the "blue" species migrates into the territory of the "red" species, they often find they can't interbreed anymore. Too many genetic differences have accumulated. Yet since interbreeding is possible all the way from red to blue, we don't know whether to consider them separate species or one big species. All that it takes for this group to separate into different species, is for some intermediate species to go extinct. This has happened in nature. Ring species illustrates how concept of species is arbitrary "in a cosmic context" (to quote Dr. Moore), but is meaningful in human context.

Transitional species

Many people imagine transitional species to be something akin to a mythical crocoduck kirkcameronii (here Moore showed a picture with a head of a crocodile and body of a duck). This, of course, is not what transitional species are like. A real example would be Achaeopteryx lithographica, a primitive bird with a lizard tail. It has wings and feathers.

How do you get from a fish to a tetrapod? Most people think there must have been something fishy-like that grew legs. But we haven't found a good example of it until discovery of Tiktaalik roseae in 2006. This shows predictive power of evolution. Scientists were able to predict in what type of rock, what type of location they could find something like this -- a fish-like creature with appendages resembling legs. It has a tail with fins, it also has gills. But the front fins were very different: they had primitive wristbones. It could push itself up with them. It also had a very unfish-like head, and a neck.

Another remarkable transitional species is Ambulocetus natans, a walking whale, discovered in 1996. It's a mammal that's perfectly adapted for aquatic life.

Molecular evidence

While the subtle points of the argument might have escaped me, the gist is that similar molecular sequences in ubiquitous genes indicate a genealogical relationship between species.

Pictures from Darwin Day can be found in my photo gallery. I will keep adding new pictures in the days to come.

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ArmadilloCon 2008: Getting the Biology Right in SF

On "Getting the Biology Right in SF" the panelists skewered writers for common biology-related blunders we see in books and movies. The aspects of biology covered in this panel ranged from human anatomy and physiology to ecology.

As an emergency room physician, Kimberly Frost was uniquely qualified to educate writers on what kind of injuries a protagonist could sustain and still survive. One of the highlights of the panel was her showing the audience how far her blood would spurt if the arteries in various places of her body were cut. The panelists noted that there are lots of individual differences in how much bodily damage a person can incur and survive, but feats like jogging 500 miles with a gushing wound (one of the panelists has actually read a story where this happened) is flat out impossible. Yet human body is capable of less ridiculous, but still impressive performance under duress. Paige Roberts told a story about her ex-husband, who had half of his right hand blown off by enemy fire; the bullet severed the nerves that controlled the two outermost fingers, but he still had control of his index finger. So he clamped the wound down with his other hand and kept shooting, and saved a dozen soldiers' lives. In a few hours, though, he was flat on his back in a helicopter, being medevac'ed. Adrenaline can only take you so far.

Kimberly Frost has first-hand familiarity with what happens when movies and books use medical facts irresponsibly. For example, too many times in the movies you see people breaking the glass with their limbs when they want to break into a house or out of it, and the glass just breaks away. But in reality it doesn't work that way. Kimberly has seen people who tried to do it: some of them cut themselves only superficially, and doctors were able to fix them up, but others cut their tendons that way. Paige writes erotica, and she is careful not to give readers ideas to try things that would be very dangerous in reality -- like bondage with a rope tied around one's neck.

Later Paige Roberts and John Moore got into an animated argument on whether the difference between your and opponent's body mass is a deciding factor in winning a fight. John Moore argued that it was; Paige, who's done martial arts, thought other factors matter more. She said she would have little difficulty throwing a tall, muscular guy across the room, but would find it impossible to do the same to a short person with a low center of gravity.

On the ecology front, one the most interesting observations was the one Kelly Persons made about Frank Herbert's "Dune". "Dune" is often praised for its ecological theme, but the problem with Dune is that it doesn't have any ecology. "It's a planet with one species on it. There's no energy input into the Dune world," Kelly said. It takes a lot of energy to power a worm that's as big as a locomotive to move underground. What did worms eat? And where does the oxygen come from, given that it's a desert planet? John Moore asked.

Why is carbon, not silicon the basis of life? was a question from the audience. Because, says Kelly Persons, carbon is able to form long chains, while silicon can't. A combination of silicon and oxygen can form long chains, but only under certain conditions. If you are writing about an alien silicon-based life form, the temperatures on the planet where it evolved would have to be very different.