The theory of evolution was the greatest discovery in 19th century biology that associated with species classification, distribution, and comparative anatomy in natural history. In the future, genetics and molecular biology will improve it into a tool for exploring the origin of life. How did Charles Darwin transform from a Christian theologian into a naturalist who changed the course of human history? All of this originated from a wondrous voyage that lasted 5 years.
The Voyage of the Beagle
Charles Darwin majored theology at Christ College Cambridge, but he was also very interested in natural science. The most significant event was that he met botanist John Henslow and became his close friend and adherent through his cousin William Darwin, an avid beetle collector. It was Henslow who recommended Darwin to Robert FitzRoy, the captain of Beagle, as an unpaid conversation partner.
The Great Chilean Earthquake
During the voyage, the vast geological changes depicted in Charles Lyell's book opened up an entirely new perspective for Darwin to reexamine the world. Thus, every time the Beagle docked at a coast, Darwin was there to observe geological phenomena. The Chilean earthquake left a deep impression on him. Throughout the cities and villages, there were ruins of collapsed houses and walls. Countless chairs, tables, and bookshelves were scattered across beach, and whole roofs of several farmhouses were moved to coast. Bags of merchandise strewn on beach from some torn-apart warehouses.
In the face of nature's might, not only was the prosperity of a nation as fragile as paper, but even the ground itself, once a symbol of stability and solidity, was like a thin shell floating on the restless magma sea. In many places, the ground had cracks running from north to south. Near the cliffs, some fissures were even a yard wide. The surface of some ridges was completely shattered, as if blasted by gunpowder. The land around the bay had been uplifted by two or three feet: a small rocky shoal now exposed had been underwater previously. Santa Maria Island was thrust upward more obviously. Darwin found numerous rotten mussels clinging to rocks over ten feet above watermark. Before the earthquake, locals would dive to dig these mussels after tide receded.
At Valparaíso, similar shells could be found in places as high as thirteen hundred feet. There was no doubt that this area was a sea in ancient times. The repeated uplifts of several feet at a time turned it into a towering mountain. Earthquakes and volcanic eruptions happened every few hundred years, so this process must have continued for millions of years, or even longer. This seemed inconsistent with the unchanging world in Bible that was only a few thousand years old.
Peculiar modern and ancient creatures of South America
The Giant Fossils of Ancient Creatures
Darwin discovered the fossils of several enormous ancient creatures in Pampas of Argentine. Besides the giant ground sloths, there was a large animal like camel, some fossils with armadillo-like skeletal armor but much larger, and even a skull of giant mice that was far larger than any modern ones, and so on. It was generally believed that species created by God were immutable. However, Darwin speculated that smaller modern creatures might be their descendants, according to these fossils.
Greater Rhea and Lesser Rhea
The South American continent also had a species similar to ostrich and emu, known as the rhea. The Greater rhea inhabited regions close to the Pampas of Brazil and the La Plata basin. They were adapted to low altitudes and warm climates. When Darwin explored the southern Patagonia plateau, a companion shot a bird like juvenile greater rhea. It was not until he had eaten it that he remembered the locals had said there was a smaller rhea. Fortunately, the head, neck, legs, wings, feathers, and skin were preserved. When beagle returned England, it was made into a specimen exhibiting in museum. It was named Lesser rhea or Darwin's rhea. It was adapted to cold, high-altitude environments where wastelands were covered by low shrubs and grasses. Though their primary habitats did not overlap, both rheas lived in the transition region from Pampas to Patagonia plateau. Why would God create two different birds in such a close area and make them compete? Is this a waste of time?
How Darwin proposed Evolution Theory: Natural Selection, Survival of the Fittest
In October 1836, he returned to the starting point—Falmouth, England. Darwin never expected that he soon transformed from a graduate to a naturalist. During the five-years voyage, Henslow had shared their letters with a number of British naturalists. Darwin was already famous in British academic circles. Lyell even became a lifelong friend of Darwin and helped him gain membership in the Royal Society of London. From then on, Darwin had plenty of time to pursue his passion.
Darwin's Finches in the Galápagos Islands
In 1835, Darwin collected some bird specimens on the Pacific Galápagos islands, 900 km from the South American continent. Although the finches on islands resembled those on continent, shapes of their beaks varied greatly. They did not attract Darwin's attention initially, and even the detail habitats were not recorded, until the ornithologist John Gould identified them as thirteen different species in 1837. John Gould categorized them into different groups based on the shape of their beaks. Ground finches fed on fallen plant seeds and lived in arid coastal areas. Tree finches inhabited forests. Their beaks were suitable for catching insects and opening seeds. Warbler finches had even slimmer and sharper beaks. They fed on insects on leaves and tree trunks. One of finches had beaks similar to woodpeckers, but without a long tongue. Instead, they used a cactus spine or small twig to probe for insects in tree holes.
This was no coincidence. Darwin keenly realized that one species could entirely transform into another new species. He seemed to see the ancient finches had flown from the South American mainland to the remote pacific islands and left descendants. Their beaks gradually changed in order to make full use of all the food on island. In 1837, the branching tree of animal evolution first appeared in his notebook.
Inspiration from Thomas Malthus's book
At this time, Darwin already had some vague ideas about the evolution of species and natural selection, but what gave him a sudden and profound realization was Thomas Malthus's book, "An Essay on the Principle of Population," which was read by him in 1838 to while away the hours.
Malthus believed that human population would grow in geometric progression if environmental factors were not considered. This did not happen in our real world, because the surplus labor would drastically reduce wages to result in poverty. Moreover, people would compete and clash for limited resources. War, hunger and disease would rapidly remove most of the population. Only strong survivors could obtain enough resources to live and reproduce.
Darwin suddenly realized that human society was just a microcosm of nature, and all living beings are engaged in competition. There are different traits among organisms. Favorable traits allow them to win competition, whether it is with their own kind, other species, or the environment. These traits would be inherited by next generations. Organisms with unfavorable traits would be defeated. After long periods, they would diverge from ancestors until they became a whole new species.
In fact, Darwin wrote a paper on evolution as early as 1844. Afterward, he collected a large amount of evidence from various fields to reinforce his theory. However, as an upper-class gentleman, he was very sensitive to public opinion. He was very reluctant to publish his paper in order to avoid repeating the fate of Lamarck, who was attacked by the public and the church harshly, even though Lyell urged him several times to publish in time before someone else took the fruits away.
In June 1858, Lyell’s prediction came true. Darwin received a manuscript from Wallace that described an almost identical theory. Wallace was a poor young guy, and the fucking life was fully messed up, then let the storm of public opinion hit harder. On July 1, 1858, Lyell and a colleague presented Wallace’s paper, along with extracts from Darwin’s unpublished 1844 essay, to the Linnean Society of London. Darwin quickly completed his “On the Origin of Species” and published it in 1859.