Since it has been a long time since I contributed any content to Pharyngula…here’s something. I was asked to give a brief talk on the ship, so I’ve tossed my written draft below the fold. With these short talks I like to write the story first, but when I get up on the stage and actually perform it, I don’t bring notes or anything like that, so what is actually said follows the structure of what I wrote, and some of the wording comes through, but it tends to be rather different. Probably a lot different —I know I extemporized a fair bit on the last half. This is all you get until I’ve had a good night’s sleep, though.
When Jeff Wagg asked me to say a few words up here, I was a bit concerned — that was the same day that we had the Amazing Randi and George Hrab up here, and those two are very tough acts to follow, as they actually have talent. Fortunately, Phil got up here to talk yesterday, significantly lowering expectations, and really taking the pressure off. I must thank Phil for showing that talent is completely unnecessary on this stage.
There’s still a little problem of what the heck I can say to you that does more than interfere with the rush to dinner. In particular, we have a team of naturalists here on the ship who know much more about the details of life on the Galapagos than I do, making me the superfluous possessor of abstract knowledge about evolution in general, with all these other fine people far better qualified to give you the intimate details of evolution on the Galapagos than I can. So what I think I can do here is simply introduce myself, let you know that if you have any big picture questions about biology you should feel free to ask, and I thought I’d at least try to put our little expedition in contrast with Charles Darwin’s trip.
So let me ask you — did any of you happen to see any dramatic species to species transformations on any of these islands? Did anyone notice any boobies evolving into albatrosses, or crabs turning into sea lions?
I didn’t think so. One of the difficulties of getting the idea of evolution across to people — not this crowd of course, but other people — is that it is so slow and subtle. We do not see nor do we expect to see abrupt transformations over the course of a brief, week long visit, or even over our lifetimes. Charles Darwin inferred these changes from his observations because he had two advantages over us: he was brilliant, and he was well prepared.
Darwin left England in 1831 to sail around the world on the Beagle, a ship which had the mission of surveying the coast of South America. He was not much of a sailor, so when the ship stopped at any coastal town before beginning the tedious job of plumbing the depths and taking sextant readings and all that other stuff, he’d grab a horse and go gallivanting off into the interior, promising to meet the ship at its next port of call. He criss-crossed the mainland, traversing from east to west and back again, and all up and down the continent, becoming intimately familiar with the geology and plant and animal life of South America, shipping tons of specimens back to England.
The Galapagos was an afterthought. He spent 5 weeks on these islands in 1835 while the Beagle was provisioned and repaired, after spending four years exploring the mainland. This was key: he knew very well what to expect of South American flora and fauna, so he landed here, and he noticed the strangeness in the context of what he had known on the mainland. It was familiar, but also different. Where the mainland had green iguanas climbing trees, these islands had black and red iguanas, some of which were clambering over rocks, and others that in an even more radical difference were living in the sea. There were relatively few bird species, but they resembled a subset of the ones living on the mainland, but they were also subtly different, with for instance novel specializations of their beaks that allowed Galapagos mockingbirds and finches to exploit food sources that other species of birds claimed on the mainland. What the Galapagos were to Darwin was a kind of natural experiment, where life had been isolated in a harsh environment and allowed to grow…and visibly change. We can’t see the transformation in a short visit, but we can see how life has transformed itself in the few short millions of years since these remote islands formed.
The similarities between life here and on the mainland were the product of a simple explanation: they were related. Animals and plants from mainland South America had colonized the islands shortly after they’d formed. Accounting for the differences was the clever, tricky part. That species might change over time was not a new idea — among others, Lamarck had postulated that in the 18th century — but Darwin’s new contribution was that he provided a mechanism, an explanation for HOW that change occurred. It was a mechanism that required no guidance, divine or otherwise, and that used a brutal sorting, rather than planning to generate new forms.
That mechanism is what made him famous. Natural selection is such a clear, simple idea that biologists around the world were wacking themselves in the forehead when they read his book, saying, “Of course! Why didn’t I think of that!” He laid out the facts as everybody already knew them, with simple and irrefutible logic leading to an undeniable conclusion. The members of a species exhibit heritable variability; they don’t all look alike. Not all individuals are equally successful at reproducing or surviving, and it is those variants that are best able to live under existing conditions that will leave the most offspring, meaning that the average composition of the next generation will change. Because the forms least able to thrive will not thrive, the population as a whole will slowly drift in the direction of optimality.
That’s what’s special about these islands. Evolution is an idea that explains both similarities in species, and differences. This is a place right at the interesting edge of being similar enough to the mainland that the source of those similarities, their relatedness, is apparent…but at the same time it is remote enough in space and time that the organisms here have also visibly diverged from the forms Darwin observed in mainland South America. It’s the combination of familiar similarities and uncanny differences that make the islands unique and a beautiful example of the power of evolution.