The voyage of the Beagle The year was 1831, and a young scientist named Charles Darwin was trying to decide what to do with his life. He had studied Geology in College (the study of rocks, the Earth, volcanoes, stone formations, etc.) and was thinking about becoming a Minister in the countryside. Before he did though, he wanted to see the world. He decided to sign up to be the science officer for a ship which was about to make a trip around the world – the HMS Beagle. The Beagle would be gone from England for five years before it got all the way around the world, and its mission was to explore new territory, make maps of these new areas, and report back on fossil, mineral and geologic information – Darwin was perfect for the job.

The Route The Beagle was to sail around the world to discover and map areas that had mostly been uncharted. Most of its time was to be spent in South America.

The Galapagos Islands One of the stops that Darwin made was at a group of small islands far off the coast of South America called the Galapagos Islands. These islands were very isolated because they were so far from the mainland. No animals could get back and forth from the islands to the mainland, and usually not even between the islands themselves. Because of this, the islands had many animals that were not seen anywhere else on the planet – sort of like an exotic zoo that had been sealed off from the rest of the world, and even from the other parts of the zoo. Although Darwin was a Geologist, he decided to go there and give Biology a try.

Pangaea Darwin and other geologists knew about Pangaea. Millions of years ago, there had only been one supercontinent on the planet – it was called Pangaea. Etymology (word origin) of Pangaea: From the Greek: Pan = All (examples?) Gaea = Earth (examples?)

Pangaea The Earth’s crust floats on a sea of lava. We are all floating right now, like ships at sea. Originally, there was only one supercontinent, and all living creatures lived all over it. Over time this continent broke into pieces, the pieces drifted apart. This is why Africa and South America look like puzzle pieces that have been taken apart – they actually did used to fit together. When this happened, some animals of a certain species became isolated on small pieces of land, while others of their kind lived on the large continents.

Pangaea Sometimes, the members of a species on the mainland died out, but the members on the islands survived. Darwin thought that when he got to the Galapagos he would find strange animals that had lived during the time of Pangaea, but had died out everywhere else, leaving only a few survivors in isolated pockets around the world, like the Galapagos. Think of the islands as a time capsule for ancient animal species – protected and isolated for millions of years. This was the case with many other islands like Australia and Madagascar, which each had very unique animals.

What he found… When Darwin first arrived at the Galapagos, he found he was right. He discovered a strange new type of iguana, one that actually swam in the ocean and ate seaweed.

Marine Iguanas

What he found… He also discovered several other types of animals, such as the Galapagos Tortoise, which is the world largest tortoise at about 650 pounds, and can live for about 200 years. In fact, when Darwin was on the islands in 1830s he took a baby tortoise named Harriet home with him. She lived to be 175 and only died in 2006! Darwin also found new types of seals and penguins, and a new type of Finch.

Tortoise

Penguins

Seals

Finch

Exploring the other islands… Darwin was happy, and kept doing research from one island to another. Soon, however, he found something that confused him. Each island had finches, but they were all different. Each island had one type of finch, and that type was found nowhere else – not on the other islands, and not on the mainland. As Darwin sailed from one island to another (which were too far apart for a finch to fly) he found that each island had finches that were similar to each other, but were each in some way unique. Why could this be?

The Problem… This did not make any sense, because: 1 - If one type of finch had been on these islands during the breakup of Pangaea millions of years ago, then all the finches should all be the same as each other, or even the same as some mainland finches… 2 - …or, if several types of finches had been on the islands at the time of breakup, then each island should have several types of finches. Why was there one type of finch per island? This problem intrigued Darwin, but he could not figure it out. He eventually recorded 14 different types of finches before continuing on when the Beagle sailed to the next stop. The question kept haunting him though… 100 Greatest Discoveries: The Start of Darwin’s Theory100 Greatest Discoveries: The Start of Darwin’s Theory

On the long and boring Pacific crossing Without much to do on the ocean voyage, Darwin kept going back to this question. “How could each island have its own type of finch? Furthermore, why was each type of finch so lucky?” Why did he think they were lucky? Because each type happened to end up on an island that had the right kind of food for it. For example, the finches with large beaks lived on the islands with nuts and seeds for food, and they used their large beaks to crack into them. The ones with long beaks lived where flowers had a lot of nectar, and they could reach it with the long beaks. The ones with sharp beaks lived where they could catch bugs that were flying around. The ones with strong beaks lived where insects could be drilled for through tree bark, and so on…

Eureka! “Why are these birds so darn lucky to live where they had the perfect food source?” If they were each on different islands they would starve and die. For example, if the birds with long beaks ended up on the nut island, they would not be able to crack the shells for food, and the entire species would die out, right? “Well, perhaps one or two could survive if they happened to have long beaks that were also strong…” …and that simple piece of reasoning solved the problem for Darwin, and helped him discover one of the most important concepts in science and history.