A VISIT TO THE GALAPAGOS ISLANDS
This is a missive about Steve's 'religious pilgrimage' to the holy land of Charles Darwin.
In November, 2013 we went to the Galapagos Islands on a Silver Seas cruise. It is necessary to go on a cruise because most islands are uninhabited by humans and camping is not permitted. We flew from Quito, Ecuador to the airport on Baltra, one of the islands, and were taken by small boat, a Zodiac, to our cruise ship. The Galapagos Islands, an isolated volcanic group like Hawaii, are both a province and a national park of Ecuador and access is rigidly controlled in order to preserve the natural characteristics of the plants and animals. The islands lie about 600 miles straight west of Ecuador astride the equator. They were ďdiscoveredĒ by a Spanish bishop, Fray Tomas de Berlanga, in 1535 when the ship he was sailing in along the west coast of South America was becalmed and the Humboldt Current carried him further west where he ran into the islands by chance. The sailors noticed two things: the birds and animals were astonishingly tame. They did not fear humans at all and were easy pickings for hunters. The islands also lacked fresh water with one exception. The sailors were most interested in finding water, which they finally did and left.
Subsequent to this ďdiscoveryĒ the islands attracted whalers and pirates for a couple of hundred years. They hunted the animals for food, but apparently did not do this for long enough to cause the animals to learn to avoid humans. A few towns were established but most islands have no permanent human habitation. When Charles Darwin arrived in the Beagle in 1835, the animals were still remarkably docile as they are today. So we sailed where Darwin sailed, walked where Darwin walked, and saw what Darwin saw. We sailed to several islands on our ship and then were transferred to shore in small Zodiac boats. Landings were dry when there were appropriately sized lava flows to jump onto. Otherwise the landings were wet. We would approach a beach and get out in water about a foot deep and walk ashore. Most of the islands have no docks and will not ever have any.
A striking observation is the continued docility of the animals: birds, reptiles, invertebrates, and mammals. The birds do not take flight as a group of humans approaches. The iguanas donít run and the sea lions asleep on the beaches continue to sleep. In the highlands of Santa Cruz island where we find the giant tortoises, these creatures donít withdraw into their shells when a noisy group of travelers comes to watch and photograph them. After visiting a few islands one also notices that many of them have unique flora and fauna. One sees red-footed boobies on one island and blue-footed boobies on another. Some types of trees are present on only one island. Darwin noticed this and proposed that seeds, logs, and rafts of vegetation carrying some animals with them had been carried from South American rivers to the Pacific and then by the Humboldt Current to land on one island and not another. He did experiments to see how long seeds could survive in salt water or in the mud on the feet of birds and convinced himself that the journey across 600 miles of ocean was possible for the species that made it to the Galapagos. One is struck by the observation that the islands are populated only by animals who can either swim or fly. Some of the islands inhabited by humans do have dogs, cats, and rats but there are ongoing efforts to eradicate those that have become wild and upset the ecology by predation. Darwin actually asked himself why there were no horses, sheep, or cattle. If God had created everything in the manner indicated in Genesis, then he could have put all the various creatures everywhere. But that is not what Darwin saw. In his Beagle voyage he noticed that the flora and fauna of islands close to a continent were quite similar to the flora and fauna of the adjacent land mass. In contrast, the flora and fauna of remote islands were very restricted, often odd combinations, and even unique from island to island. This was obvious to us on our visit.
We didnít see enough finches to make Darwinís observation about beak shape and food source but Darwin didnít make this connection immediately either. What we did see was a group of ecological systems that were relatively self-contained.
Each island was its own microenvironment: unique plants, birds, and animals. Some birds and sea lions could obviously move from island to island and they did but I was impressed by how many birds particularly seemed to prefer just one or a couple of islands to set up a nest. One can also notice the small changes in animals that led Darwin to propose descent with modification as the mechanism of speciation. The example that struck me was the difference between red-footed and blue-footed boobies. These birds are the same size and differ only in foot coloration and one behavioral feature. The blue-footed boobies make their nests on the ground while the red-footed boobies, who also have webbed feet, make their nests in trees. They grasp branches with their webbed feet just like other birds that donít have webbed feet. I asked the naturalists if the bone structure of the blue feet and red feet were noticeably different but they didnít know. I didnít propose killing one of each in order to examine their feet more closely. But this sort of minimal change is exactly what Darwin noticed that gave him the idea that species were not stable and gradually varied until they became new species. Twenty years later Alfred Wallace noticed the same thing in the East Indies.
Darwin did not immediately conclude that evolution was the cause of speciation when he was on the Galapagos in 1835. After he came home to England he began thinking about what he saw. He began to write books about various topics in biology. Then in 1838 he read Thomas Malthus who proposed that all species could be forced to compete with each other for survival when resources became limiting. It was this idea that stimulated Darwin to propose natural selection as the mechanism driving speciation. Just as a farmer could breed animals for desired characteristics, Nature could select animals that had features more suitable for survival in any given environment. And, when environments changed, so would species. Even after reading Malthus in 1838 Darwin did not publish his idea until 1858 when he and Alfred Wallace sent a joint letter to the Royal Society proposing that species were not stable as was commonly believed at that time. Wallace wrote that species tended to vary continuously and Darwin wrote that the driving force for this instability was natural selection acting on naturally occurring variation. Some variants would have advantages over others when resources were limiting or when predation changed. One could easily see this on our trip by comparing red and blue-footed boobies, one that nests in trees and one that nests on the ground. If iguanas or any other ground based animal developed a fondness for boobie eggs, the blue-footed birds would be at a disadvantage and the red-footed variety would gain a relative advantage. Indeed we saw a lot more red-footed boobies on the islands we visited. Some have no blue-footed birds at all. I doubt if I could have figured out what Darwin did after an accumulation of such clues but thank God, he did.
I should also mention that the crew of the cruise ship was composed of wonderful, gracious people. The naturalists aboard who guided our shore visits were very well-informed and delighted in answering our questions. The food, all Ecuadorian in style, and wines from Argentina and Chile were also great. One Ecuadorian custom is to put popcorn in ceviche. Itís pretty good.
This trip was a bucket list item for me and we both loved it. We would recommend that one devote an entire week to the Galapagos and not try to cram in a visit to Cusco and Machupicchu right afterward as we did. The Galapagos and the Inca capital and ruins should be separate trips.