Charles Darwin, 1 of the most influential figures in the history of science, fundamentally altered humanity’s understanding of life on Earth. His theory of evolution by natural selection provided a powerful and elegant mechanism to explain the immense diversity of species. Born on February 12, 1809, in Shrewsbury, England, Darwin’s early life was marked by a deep and abiding curiosity about the natural world, a passion that would ultimately lead him to a revolutionary scientific discovery.

Dreams Change

Despite his family’s initial hopes for him to become a doctor or a clergyman, Darwin’s true calling lay in the study of nature. He attended the University of Edinburgh to study medicine but was repelled by surgery. He later enrolled at Christ’s College, Cambridge, with the intention of becoming a parson. However, his time at Cambridge was spent pursuing his botanical and entomological interests, and he befriended several prominent naturalists who encouraged his passion. This period of academic exploration and mentorship was crucial in preparing him for the journey that would change his life and the course of science.

The Journey Begins

In 1831, Darwin was offered a position as a naturalist aboard the HMS Beagle, a vessel tasked with a 5-year surveying expedition around the world. This voyage proved to be the most significant event in his intellectual development. The ship sailed to South America, Australia, and various islands, allowing Darwin to collect a vast number of specimens and make detailed observations of the geology, flora, and fauna of each region. He meticulously documented everything he saw, filling numerous notebooks with observations that would form the basis for his later work.

Similar, but Different

The expedition’s visit to the Galápagos Islands was particularly formative. Darwin observed that the plants and animals on these isolated volcanic islands bore a strong resemblance to species on the nearby South American mainland, yet they had unique characteristics. He was especially intrigued by the different species of finches he found on different islands, noting variations in their beak shapes. While he initially dismissed the significance of these subtle differences, his observations would later become a cornerstone of his evolutionary theory.

The Real Work Begins

Upon his return to England, Darwin spent years poring over his collections and notes. He realized that the differences he observed in the finches, mockingbirds, and tortoises of the Galápagos were not random; they were adaptations to their specific environments. For instance, finches with stronger, thicker beaks were better suited to cracking open hard seeds, while those with slender beaks were more adept at catching insects. This observation led him to question the prevailing belief in the immutability of species.

The Beginning of a Theory

Darwin began to formulate his theory, but he did not work in isolation. The naturalist Alfred Russel Wallace, who was independently developing a similar idea, sent Darwin a manuscript outlining his own theory of evolution. This spurred Darwin to finally publish his own extensive work. Their joint papers were presented to the Linnean Society of London in 1858, and in 1859, Darwin published his groundbreaking book, On the Origin of Species by Means of Natural Selection.

The Principles

The core of Darwin’s theory rests on a few key principles. First, there is variation among individuals within any species. Second, these variations are heritable, meaning they can be passed from parents to offspring. Third, organisms produce more offspring than their environment can support, leading to a “struggle for existence.” Finally, individuals with variations that give them an advantage in this struggle are more likely to survive, reproduce, and pass on those favorable traits to the next generation. This process, which Darwin called natural selection, leads to the gradual change of species over time.

The Proof is in the Moths

A classic example of natural selection is the peppered moth (Biston  betularia). Before the Industrial Revolution in England, most peppered moths were a light, mottled color, which provided camouflage against the light-colored lichens on tree trunks. A small number of dark-colored moths existed but were easily spotted and eaten by birds. However, as factories began to spew soot into the air, the tree trunks darkened. The light moths were no longer camouflaged and became easy prey, while the dark moths now blended in and had a higher survival rate. Over time, the dark form became more common in polluted areas.

The Adaptation of Finches

Another compelling example comes directly from Darwin’s observations of the finches on the Galápagos Islands. The islands presented a variety of distinct ecosystems, each with its own food sources. Some islands had an abundance of hard, tough seeds, while others had soft seeds or insects. Over many generations, finches on islands with hard seeds evolved thicker, stronger beaks, while those on islands with smaller seeds developed smaller, more pointed beaks. The varying beak sizes were a direct result of natural selection favoring traits best suited to the available food.

Bacteria

A more contemporary example of natural selection is the development of antibiotic resistance in bacteria. When an antibiotic is used to treat a bacterial infection, it kills most of the bacteria. However, a small number of bacteria may have a random genetic mutation that makes them resistant to the drug. These resistant bacteria survive and reproduce, passing on their immunity to their offspring. As a result, the population of resistant bacteria grows, making the antibiotic less effective for future infections. This rapid evolution of resistance is a perfect illustration of natural selection in action today.

The Book that Changed Everything

On the Origin of Species was met with significant controversy upon its publication, as it challenged the prevailing religious and scientific views of the time. However, Darwin’s painstaking research and meticulous documentation provided a compelling argument that gradually won over the scientific community. His theory offered a unified explanation for the patterns of life observed across the globe, from the fossil record to the geographic distribution of species.

In Conclusion

Charles Darwin’s life and work represent a monumental achievement in human intellect. His theory of natural selection not only provided a scientific explanation for how species evolve but also laid the foundation for modern biology, genetics, and ecology. His legacy is not just in his theories, but in the rigorous, evidence-based approach to science that he pioneered. Through his keen observations and revolutionary insights, Charles Darwin forever changed our perspective on the history of life on Earth.