Richard Dawkins: Saddles and Domes: Evolution of the Giant Tortoises
Richard Dawkins explains how and why the Giant Tortoises of Galapagos evolved on each of the different islands. He shows how the different shell shapes evolved to help the tortoises adapt...
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[waves splashing] Richard Dawkins: When we find similar but distinct types, like the Galápagos giant tortoises, on different islands of an archipelago, it suggests that traveling between the islands wasn't impossible, but it was rare. When a fertilized female or a small group happens to float by a freak accident to a new island, its descendants evolve to best survive in the new environment. The shell shape differences are evidence of such speciation. This is the Santa Cruz variety of the giant tortoise. It's one of those that has a high-domed shell as opposed to a saddle-shaped shell. It comes from lush grassland and largely grazes, evolutionarily speaking, whereas the saddleback ones live on more desert islands, and they need to reach up t...
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[waves splashing] Richard Dawkins: When we find similar but distinct types, like the Galápagos giant tortoises, on different islands of an archipelago, it suggests that traveling between the islands wasn't impossible, but it was rare. When a fertilized female or a small group happens to float by a freak accident to a new island, its descendants evolve to best survive in the new environment. The shell shape differences are evidence of such speciation. This is the Santa Cruz variety of the giant tortoise. It's one of those that has a high-domed shell as opposed to a saddle-shaped shell. It comes from lush grassland and largely grazes, evolutionarily speaking, whereas the saddleback ones live on more desert islands, and they need to reach up t...
