Monday, February 22, 2010

Amateurs on Islands

A lot of new species have evolved on islands. Sometimes these are metaphorical islands, such as spots of tundra at the tops of mountain peaks, separated from other such spots of tundra by figurative oceans of forest and plain. But usually they are literal islands. I refer not to islands that are actually chunks of continent which, like New Caledonia, carry with them entire floras and faunas. I am talking about new islands that have arisen out of the sea, whether from Darwinian coral atolls or from volcanoes. I have visited such islands: Hawaii, like hundreds of millions of other people, and the Galapagos Islands, like hundreds of thousands of other people. I got up close to some of the Galapagos inhabitants, such as a giant tortoise that I kissed (see the photo).

Islands are evolutionary laboratories, where populations can “try out” new adaptations in isolation from mainland populations. But island evolution is a lot more than just isolation. The populations of plants and animals on islands experience very different conditions from those on the mainland. In many cases this is because the animals and plants that happen to arrive on islands can “try out” new adaptations, and be amateurs. These amateurs would be soundly defeated by experts—but the experts, for whatever reason, did not arrive on the island.

One example is the woodpecker finch, one of Darwin’s finches on the Galapagos islands. This species (Cactospiza pallidus) uses sticks to pry into holes in trees and pry out insects. They do a mediocre job of it, compared to woodpeckers. But the Galapagos islands have no woodpeckers, so the woodpecker finch is able to be successful in this ecological niche.

Another example is the tree-sized sunflowers on St. Helena, and other such species on some of the California channel islands. Sunflowers, like other members of its plant family, are herbaceous plants. Their stems are not built for supporting a lot of weight, which is one reason they never grow very big. If any population of sunflowers on the mainland “tried out” growing as tall as a tree, the expert trees with strong wood (such as oaks) would shade them into extinction. But the seeds that arrived on these islands were of herbaceous plants; there were no trees to compete with the large herbaceous plants, which have evolved into trees (small ones).

If the world was one big habitat, the expert species would rule. There would be lots of species but not much room for newcomers. Because of islands, there are spaces for newcomers, like coffee house performers not having to take on Hollywood. And once in a while, new talent emerges from such islands and changes the world.

Monday, February 15, 2010

Future Evolution

Evolutionary scientists are not very good at predicting the future. They are very good at reconstructing and explaining the past.

Reconstructing and explaining the past is not as easy as it seems. Evolution has resulted from natural selection—but natural selection has acted differently on every group of organisms, and in every part of the world, and at different rates. There have been countless examples of historical contingency, as Stephen Jay Gould liked to remind us. Genetic drift and the founder effect, among other things, produced unique and unusual sets of genes upon which natural selection acted. Natural selection can only act on whatever genes are available. The story of natural selection is therefore millions of stories.

This is why evolutionary scientists cannot predict the future very well. In the past, evolution has taken millions of directions—and it will presumably keep doing so. We cannot predict the conditions of the future, nor the contingencies (accidents) that may determine which populations will be at the right place at the right time to explode into a new and dominant evolutionary lineage. When scientists try to predict the future, they make it clear that they are using their imaginations, rather than the scientific process (for example, Future Evolution by Peter Ward and Alexis Rockman). Japanese film maker Akira Kurosawa (in his movie Dreams) imagined a post-nuclear-war world with giant dandelions and people who grew horns, which was a mixture of science fiction and traditional Japanese legends.

Just because there are a million directions evolution can take does not mean we cannot make reasonable guesses about some of them. I invite your comments about what you think some of the future directions of evolution might be.

Tuesday, February 2, 2010

Natural selection of fiction

I teach and write books about evolution. I also write fiction. I have published little of it, in magazines that were obscure before becoming extinct. My fiction is sometimes about evolution (about Neanderthals, or about Homo ergaster hiding in Madagascar), but usually not. What overlap is there, then, between my two spheres of writing? Is fiction just an escape?

No. There is plenty of science even in the fiction that is primarily about something else. First, all of my fiction is pervaded by the awareness that all of the action is taking place in a scientifically-comprehensible universe. In this sense, I like to think that my writing resembles that of the late John Updike. He read about science, and was particularly interested in Mars (he wrote about it for National Geographic and has appeared in Best American Science Writing 2004). His novels and stories were never, as I recall, about science (a minor character in Couples was a scientist who studied photosynthesis); they were usually about networks of people having sex. But particularly in his later works the science showed through. In his millennial novel Toward the End of Time, the narrator (of course, a lecherous older man) walked toward the bathroom in the middle of the night, seeing light through the slit of the bathroom door—and it reminded him of the photon slit experiment that showed the dual nature of light.

In this regard, my bĂȘte noir is writers who are almost proud to know nothing about science. I have encountered two instances in which a writer thought that thunder traveled faster than lightning. I don’t expect writers to be able to recite the Central Dogma in Latin or anything, just to know that light travels faster than sound.

Second, a good story is the product of natural selection. The characters and events have to work within the environment in which they take place. The events and the characters are designed by the author, but they have to work in a natural fashion. The environment has to be internally consistent, just as our planet has reliable laws. Even if it is not an Earth environment, it has to have natural laws, as Middle Earth did. And the characters have to interact in a way that makes sense, just as do individuals in populations and species in ecosystems. Good writers can tell if something is working or not, even though they do not explicitly call it a scientific test. They usually call it something like a bullshit-detector, which was Hemingway’s term (as I recall). My favorite example of a writer whose novels simply do not work is John Darnton (Neanderthal; The Darwin Conspiracy). Contrast this with Greg Bear. His version of evolution is all wrong, but it is consistent in his created world.

What examples can you think of?