In 1831, a young, English naturalist named Charles Darwin boarded a ship called the Beagle. He was headed on a five‑year expedition. His task? To collect and study animal, plant, and rock samples. Darwin would become one of the most famous scientists of his time. He contributed to the theory of evolution. He proposed that all living things have descended from common ancestors.

What is less well‑known about Darwin is that he was prone to seasickness. As a result, Darwin was always the first to go ashore and the last to leave it. Because of that, his collection of samples was both large and diverse.

Darwin took many notes and kept a journal. Along with the logs of the Beagle’s captain, Robert FitzRoy, they help us to know exactly where they traveled and what they collected.

The Beagle reached the Galápagos in 1835 and spent five weeks there. Darwin visited four of the larger islands. San Cristóbal was first. Made up of four extinct volcanoes, it is home to the oldest permanent settlement of the islands.

San Cristóbal’s dry, rocky coast was not what Darwin was expecting. The island seemed devoid of life. He found patches of desert plants. In a partly vegetated lava field, he found two enormous tortoises. They were grazing on cactus. Here, Darwin collected the first species that would become the foundation of his theory, the San Cristóbal mockingbird.

Floreana was the second island to be explored. Darwin spent three days here collecting samples. These included a second important bird, the Floreana mockingbird. The distinct differences between this bird and the one found on San Cristóbal prompted Darwin to pay close attention to Galápagos birds.

On Floreana, Darwin also met with a fellow Englishman named Nicholas Lawson. He was the acting governor for the island. Lawson told Darwin that he could identify which island a tortoise came from. How? By looking at its shell. Each island’s tortoises were different, he said. Darwin wondered about that.  

The volcano that is Isabela Island was erupting when Darwin explored it. He observed lava flows and smoke coming out of craters. He took detailed notes and collected land iguanas.

It was Santiago Island where Darwin stayed the longest. Here he saw what Lawson had described: The tortoises were different. Darwin had collected vast amounts of samples. Yet, he didn’t understand what he was seeing.

Of the mockingbirds, he could see four different species, each from different islands. The finches he’d collected seemed to be different, too.

Darwin gave the samples to the ornithologist John Gould to examine. Gould found that they were different enough to justify at least 14 species. Darwin would ponder this for years.