The Tortoises of the Galapagos
Posted on Oct 6 2011 at 06:00:43 AM in Earth & Geography
Perhaps one of the most significant creatures to influence Darwin in constructing his theory of evolution was the humble tortoise. The giant tortoise of the Galapagos, to be precise. When Darwin first arrived at the Galapagos islands in the early 19th century, some of the first creatures he noticed were these innocuous, giant tortoises, who lived peacefully within small communities scattered all over the islands.
However, it wasn’t the size of these creatures that first caught the attention of the then-young Darwin. Darwin noticed differences in the shells of the beasts, differences that were consistent with whatever island the creatures were living on. He noticed that there were two main specimens of the Galapagos giant tortoise inhabiting the islands: the first of which had a thicker shell with a lower neck arch, the second had a thinner shell, but with a much more generous neck arch. He also noticed that the former inhabited an island abundant in low shrubland and grass, but also predators. Darwin observed that the second kind of tortoise lived on the drier isles that were sparse in grass, but offered more shrubs and grassy bushes, but with much less predators. This discovery led Darwin to realise that the differences were not just random, but had come from some kind of form of geographic selection. Not that each type of tortoise had migrated to its own comfort zone depending upon physical characteristics, but rather that the ecological differences of the island had shaped and sculpted the generations of tortoises inhabiting them. This, he called, evolution, which is arguably the most important scientific discovery in any field to date.
If you’re interested in discovering the roots of evolution, the I suggest you do what I did: volunteer in Latin America and see the Galapagos for yourselves. You too can come and see the very place that nurtured and acted as the muse of Darwin’s theory. The giant Galapagos tortoises are still there today and are still prolific amongst the isles. You will be able to see how their diversity has been sculpted via geographic and natural selection, with more or less the exact same picture Darwin himself was looking almost two centuries ago. Similar fauna can be found if you volunteer in Guatemala.