The Great Eukaryotic Melee

Cat fight! Mrowwwr! Hisssssss!

Every now and then, you can capture a snapshot of the scientific process at its worst (and paradoxically, its best, too). The trick is to look at the Letters or Perspectives section of your favorite scientific journal.

In this case, I happened to come across an argument between two sides in what I will call the Great Eukaryotic Melee (there are probably more than just two sides in this debate, but only two are reflected on these pages). Actually, the debaters seem to be rather more well-behaved than I suggested above, but it is true that these fights do sometimes turn ugly.

The central issue? How did Eukaryotes evolve. Let’s review some basics.

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Watching the Watchmaker

There is an old argument that creationists like to trundle out from time to time, called the Watchmaker Argument. It’s been roundly defeated by evolutionary biologists (many times over), but I’d like to address a part of it that most modern evolutionists skip over, because it’s an interesting philosophical exercise.

In 1802, William Paley published, Natural Theology, which was an extended argument in favor of the existence of God, and a refutation of the current ideas about evolution. Astute readers might have noticed that 1802 was 57 years before the publication of On the Origin of Species by Charles Darwin. In fact, Darwin took the arguments in Natural Theology very seriously and went to great lengths to refute them. I suppose he might have had it in front of him while he composed his treatise, although I’m not enough of a historian to say.

Anyway, the central argument of Natural Theology goes like this. Say you’re walking along, thinking evolutionary thoughts to yourself, when you come upon a pocket watch. The watch was probably planted there by a creationist, but that’s neither here nor there. Anyway, you pick up the watch and examine it, and immediately understand that it is a complex device that was been made by a watchmaker. It did not just pop up out of the ground like a stone.

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Anolis urbis

Move over, moths! There’s a new kid in town!

During the Industrial Revolution, naturalists in England noticed that the incidence of normal, light-colored peppered moths (Biston betulari) had become scarce in the vicinity of various urban centers. Instead, they were finding a melanistic (dark colored) variety. At the same, time, pollution had caused the local trees to get darker. In 1896, J.W. Tutt proposed that this change was an example of natural selection. The light moths lost their camouflage effect when they sat on the new dark trees, so they got eaten by the local birds. Hence, the moths with the gene for melanism fared better and became prevalent.

The issue was hotly debated and thoroughly investigated through the first half of the twentieth century, and has since become one of the best known and best supported examples of natural selection. You probably remember it from your high school biology class.

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Bracketing the Past

How do we learn about extinct things? Can we use evolutionary theory itself to help us? Yes, but first we need to take a heuristic detour into space.

Suppose you’re an alien from another star system, maybe a thousand light-years from ours. Your scientists pick up radio wave transmissions from Earth, but they are garbled. You know there’s a civilization here, and you can figure that the transmissions came from the third planet, but you don’t have much more detail yet. So, you pack up your spaceship and head over our way.

Unfortunately, in the intervening time, us silly humans manage to blow up the Earth. When you arrive in the Sol system and come out of cryosleep, all that’s left here is a shiny new ring of asteroids where our big blue marble used to be. (Sigh …it happens.)

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Dinosaurs Quadrupedal

Well, the time has come to talk about dinosaurs. In a blog about evolution, it was inevitable. Dinosaurs are, so to speak, the elephant in the room.

It is widely believed that dinosaurs are big and go “Rawr!’. While it is certainly true that dinosaurs go “Rawr!” (of course, there’s a Santa Claus, boys and girls!), it happens that many were not very large.

Some were, of course, brain-meltingly huge. But others were the size of a chicken. In fact dinosaurs came in such a diversity of sizes and shapes, that talking about dinosaurs is a bit like talking about mammals: there are just too many of them to be able to generalize much. Mammals can be giant like an elephant – or a whale – or they can be tiny like a shrew. And they’ve changed dramatically over evolutionary time. Same thing with dinos: the first dinosaurs were quite different from the ones that got smacked down by that asteroid at the end of their reign.

But there’s one thing that seems to have remained the same over the entire age of the dinosaurs: the carnivorous ones always had a bipedal stance. From Allosaurus to Velociraptor, they all seem to have run on two beautifully engineered legs. Herbivores came in a surprising array of shapes both two-legged and four; but carnivores? Just the two-legged variety.

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