How did Darwin propose the theory of evolution by nature selection?

Charles Darwin is widely recognized as the main creator and primary contributor to the theory of evolution. His book "On the Origin of Species," revolutionized the field of biology and had a profound impact on our understanding of the natural world.

The voyage of the Beagle

In 1831, Darwin embarked on a five-year journey on the Beagle as a self-funded adventurer. During this journey, he traveled through South America, Australia, New Zealand, Africa, and the Pacific islands. He collected numerous specimens along the way, and meticulously documented his observations in his log. These specimens and log provided strong evidence for the theory of evolution.

During his journey, several experiences left a deep impression on him. He experienced a violent earthquake in Chile, which lifted the seafloor several meters. He discovered fish and shell fossils at high altitudes in the Andes Mountains, indicating that the area was a sea in the past. Darwin believed that ancient sea might have experienced multiple earthquakes that made the sea floor rise into mountains. Although each uplift was only a few meters at a time, the cumulative changes over hundreds of millions of years could give rise to a towering mountain. It seemed incompatible with the biblical timeline of only a few thousand years.

He found fossil of giant ground sloth that closely resembled the skeleton of modern-day sloths in South America, although the ancient sloths were much larger. Darwin speculated that they might be closely related. He also discovered two species of ostrich-like birds in South America, similar to the ostriches of Africa and the emus of Australia.

One of the significant observations Darwin made was in Galápagos Islands. He found that different finch species had distinct beak shapes adapted to different diets. However, all finches on Galápagos Islands were similar to the finches of the South American mainland.

The creation of evolution, natural selection

In the face of species diversity, kinship, and the ever-changing geologic landscapes, Darwin gradually began to doubt the theory of divine creation. He had read the book wrote by Thomas Malthus, "The Principle of Population." When the population becomes excessively large and resources become scarce, people engage in competition, conflict, and even war to redistribute resources. The victors gain sufficient resources and continue to reproduce. Darwin applied this view to his evolution theory and successfully explained the unity of life and diversity of life.

He believed that there were different characteristics among organisms. Through competition, or natural selection, organisms with more advantageous characteristics were survived and their characteristics passed on to offspring. He proposed that species change over time, and new species arise from ancestral forms through a gradual process of descent with modification.

Darwin actually wrote a paper about evolution as early as 1844. After that, he gathered extensive evidence from various fields, including comparative anatomy, paleontology, embryology, and biogeography, to reinforce his theory. However, he refrained from publishing it to avoid public backlash, even though his friends repeatedly urging him to publish it promptly to prevent others from taking credit. It was not until a day in 1858 when he received a manuscript from Wallace, which described a nearly identical theory. Darwin graciously shared his research findings with Wallace. Following this event, he promptly completed and published "The Origin of Species" in 1859.

Frequently Asked Questions

How the diversity of finches develops?

In search of more food, the finches accidentally arrived on this small island from the South American mainland. Some with elongated beaks were able to catch more insects, while the others that couldn't find insects resorted to eating flowers and seeds. The individuals with advantageous traits were more likely to survive and reproduce, while those with adverse traits were less successful and eliminated by nature. The higher the proportion of advantageous traits in the offspring, the less the proportion of adverse traits. Eventually the advantageous traits dominate and new species are formed.