"In the morning (17th) we landed on Chatham Island, which,
like the others, rises with a tame and rounded outline, broken here and there
by scattered hillocks, the remains of former craters. Nothing could be less
inviting than the first appearance. A broken field of black basaltic lava,
thrown into the most rugged waves, and crossed by great fissures, is everywhere
covered by stunted, sunburnt brushwood, which shows little signs of life. The
dry and parched surface, being heated by the noonday sun, gave to the air a
close and sultry feeling, like that from a stove: we fancied even that the
bushes smelt unpleasantly." Chapter XVII - Voyage of the Beagle
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| From Darwin and the Beagle, A. Moorehead 1969 |
In this podcast Josh, Sarah and James talk about Darwin's visit to the Galapagos Island and how that experience ultimately contributed to Darwin rejecting the notion of the fixity of species and developing his theory of the evolution and the process to create new species. The Galapagos islands are a chain of volcanic islands that poke out of the Pacific ocean over 500 miles off the coast of Ecuador. Although many of the islands are relatively close to each other, Darwin was struck by how the plants, insects, birds and reptiles on each of the islands were distinctly different from the other islands.
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| Bartolome Island, Galapagos Islands, Travel Channel |
Although most people associate Darwin and his experience with the Galapagos finches in developing his theory of evolution, we make the argument that it was the Galapagos tortoises that first intrigued and befuddled Chuck and stimulated him to begin pondering
"...that mystery of mysteries—the first appearance of new beings
on this earth."
In the Voyage Darwin writes-
"I have not as yet noticed by far the most remarkable feature
in the natural history of this archipelago; it is, that the different islands
to a considerable extent are inhabited by a different set of beings. My
attention was first called to this fact by the Vice-Governor, Mr. Lawson,
declaring that the tortoises differed from the different islands, and that he
could with certainty tell from which island any one was brought. I did not for
some time pay sufficient attention to this statement, and I had already
partially mingled together the collections from two of the islands. I never
dreamed that islands, about fifty or sixty miles apart, and most of them in
sight of each other, formed of precisely the same rocks, placed under a quite
similar climate, rising to a nearly equal height, would have been differently
tenanted; but we shall soon see that this is the case."
Josh talks about Darwin's experiences with these cyclopean creatures, drinking from their bladder and riding them like a horse, and about recent efforts to determine how many different species of tortoises actually exist and the current conservation efforts to protect them.
The image of Darwin riding a tortoise reminded us of the old sketch a friend of Darwin's made showing Charles Darwin riding a beetle.
Sarah talked about the marine and terrestrial iguanas found on the islands and how Darwin would throw the marine iguana into the ocean for it to rapidly return to shore wherein Darwin picked it back up by the tail to fling it back in the ocean. Darwin repeated this "experiment" until he was convinced that although the marine iguanas were perfectly adapted to swimming in the oceans they preferred to stay on shore, where it was safe.
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| Looking out to sea - https://www.flickr.com/photos/45325473@N04/page2 |
We finished the conversation about the role of the Mockingbirds and Finches found on the Galapagos islands in convincing Darwin that different species of the same type of animal could be found on different islands, although the islands themselves were not remarkably different from each other in habitat and geology. In addition, these islands were not significantly different from volcanic islands of Cape Verde Darwin visited 3.5 years earlier off the coast of Africa, and yet the species found in each of these archipelagos were more closely related to their neighboring continents than they were to each other.
Sarah told us about her recent guest appearance on
The Common Descent which is an excellent podcast that discusses the diversity of life, past and present. Check it out!
The opening and closing theme to Discovering Darwin is "May" by Jared C. Balogh.
Interlude music Big Beats Alternative by Sunserarcher http://freemusicarchive.org/music/Sunsearcher/
