Darwin is often described – not least by himself in later years – as the ship’s naturalist during HMS Beagle’s epic voyage. However, he wasn’t. Beagle did indeed carry an official naturalist but it was the ship’s surgeon, Robert McCormick. Darwin, with his membership of the Linnaean Society and passion for entomology, certainly had the knowledge to act as naturalist but that wasn’t why he was on board. Instead his role was gentleman companion to the captain.
HMS Beagle was just 90 feet long and a touch under 25 feet wide, and a crew of 65 men were crammed into her smelly, claustrophobic hull. Nevertheless the captain’s existence could be a lonely one. Required by the customs of command to stay separate from his subordinate officers, he spent most of his time alone in his cabin at the ship’s stern. The solitude could lead to depression. Beagle’s first voyage after her conversion to a survey ship had to be cut short when her captain, Pringle Stokes, fell into a depression and shot himself. He was replaced by Lieutenant Robert FitzRoy, who brought the unhappy ship back to England.
When FitzRoy was ordered to take Beagle back to South America a year later his mind turned immediately to the dangers of loneliness at sea. As well as the unhappy fate of Captain Stokes he had personal concerns. His uncle, Lord Castlereagh, had cut his own throat in 1822 and FitzRoy feared that the potential for suicidal depression ran in his family. To protect against solitude he decided to take a companion on the voyage. A wealthy civilian wouldn’t be in the ship’s command structure so FitzRoy could safely socialise with him without affecting discipline.
The captain also thought it would be a good idea to find a companion with an interest in geology, so that he could examine the land while Beagle charted the coastline. After several invitations were declined he eventually interviewed, and selected, Charles Darwin. The two were from a similar social class and not too far apart in age – FitzRoy was 27, Darwin 22 – so the captain thought they would get along during the voyage. He was also impressed with the young man’s enthusiasm for science. As a gift to welcome Darwin to the ship FitzRoy gave him a copy of Charles Lyell’s book Principles of Geology.
In 1831 the general opinion was that the planet was a few thousand years old and it, and everything on it, had been created by God. That was certainly Darwin’s view, reinforced by his reading of Paley’s Natural Theology. Some geologists were starting to form a different opinion though; they observed the natural processes that shape the Earth and decided that, to produce the landscape they were seeing, those processes must have acted not for thousands but for millions of years. FitzRoy was fascinated by their argument, which he found very convincing, and gladly shared his views with Darwin.
At first Darwin was too preoccupied by seasickness to think much about geology. When Beagle reached Tenerife he wanted to go ashore, and quite possibly would have abandoned the voyage and sailed home to England. There was a cholera epidemic raging in England at the time, though, and all ships sailing from Britain were quarantined. Darwin stayed on board. At their next stop, St Jago in the Cape Verde Islands, he did get to go ashore. Here he saw, as Lyell had described, layers of rock that had been laid down over time. In the lower layers he found seashells and observed that they were, as far as he could tell, the same as present-day ones. He concluded that volcanic lava had covered the seabed quite recently and then the land had risen; at this point he was still a creationist who believed the Earth was young.
That belief became harder to support when the ship reached South America and the real survey began. Beagle worked her way slowly down the coast, her crew painstakingly measuring the depth of the seabed and plotting the coastline accurately on their charts. Darwin rejoined her occasionally but spent most of his time following her down the coast on horseback. Soon he began finding fossils of animals that were quite unlike anything that existed. Then, in the Falkland Islands, he noticed that while the fossils he found were similar to those on the mainland the living animals were rather different. He even noticed something strange about the Warrah, or Antarctic Wolf, a large fox native to the Falklands (now sadly extinct). Animals on East Falkland were bigger and tawny-brown; those on West Falkland were smaller and had a reddish colour.
Beagle sailed on. In Montevideo Darwin bought the second volume of Lyell’s book, which argued against Lamarckian evolution. Lamarck believed that animals – and people – acquired characteristics through their life and passed them on to their offspring. In a Lamarckian world giraffes stretched to reach high leaves, so their legs and necks got longer. When they had babies those would have long necks too. Darwin, the creationist, rejected Lamarckism. So did many scientists – but for very different reasons.
It’s easy to forget that Darwin didn’t actually discover evolution; by the time he was born many people already accepted that life had changed over time. What nobody knew was why, and several people – Darwin’s grandfather Erasmus was one – had tried to explain it. None of the explanations were very convincing though, and that put a lot of people off the idea of evolution. Yes, there were fossils of strange animals unlike any that now lived, but many people accepted the story that they had died in some disaster – perhaps even the Biblical flood. One of the objections to evolution was that it would have to happen very slowly, and if the world was less than 6,000 years old there simply wouldn’t have been time. However geologists like Lyell were challenging that and, already, the idea that Earth was millions of years old was catching on.
As the voyage continued Darwin slowly began to change his own views on the age of the Earth. He found or bought several fossils from Megatherium (an elephant-sized round sloth that went extinct about 10,000 years ago). Painstakingly he studied the local geology as Beagle worked her way round the southern tip of South America and up the Pacific coast. Then in September 1835, after replenishing supplies at Lima, the ship set out into the ocean for the desolate Galapagos Islands.
The Galapagos are now a famous part of Darwin’s story, but he didn’t actually have any great insights into biology while he was there. In fact he was mostly interested in their geology; the Galapagos are volcanic, and he hoped to see an eruption taking place. He was disappointed in that but did see evidence that parts of the islands had been raised from below sea level. He also collected specimens of plants, insects and birds from each island he visited. At first he didn’t separate his specimens according to the island he’d caught or shot them on, simply labelling them “Galapagos Islands”. If it hadn’t been for one chance conversation one of the greatest clues to evolution might have been lost.
Nicholas Lawson was English, but the government of Ecuador had made him acting governor of the Galapagos. Darwin happened to meet him on Charles Island, and they began talking about the islands’ distinctive wildlife. Lawson claimed that he could instantly tell which island one of the giant Galapagos tortoises came from by looking at the shape of its shell. Darwin was sceptical, but he did find a mockingbird and realise that it was different from the ones he’d seen on nearby Chatham Island. From that point he began to carefully record exactly where he’d found each mockingbird. Ironically he didn’t bother to do the same with the much more numerous finches.
Beagle left the islands on 20 October and headed for Tahiti. Darwin, faced with an extended period on the ship, started cataloguing his specimens to take his mind off his seasickness. That’s when he made a key discovery. It wasn’t just the Charles and Chatham Island mockingbirds that were different; every island he’d visited had its own species of mockingbird, found only on that island.
After leaving the Galapagos it was almost another year before Beagle finally returned to England. On the way she visited Tahiti, New Zealand, Australia, South Africa, St Helena and Ascension Island; at each, Darwin made more observations and collected more specimens. Australia’s bizarre wildlife fascinated him – it was as if, he thought two separate creators had been at work.
Darwin stepped ashore at Falmouth on 2 October 1836 and caught a coach home to Shrewsbury. He found that he was now a popular and well-known scientist thanks to the letters and articles he’d sent home throughout the voyage; he was also determined to dedicate his life to science. But he still wasn’t thinking about evolution.