On November 24, we recognize World Evolution Day, marking the anniversary of a groundbreaking paper that fundamentally altered scientific thought. On this day in 1859, Charles Darwin released his pivotal work, On the Origin of Species by Means of Natural Selection, narrating the monumental tale of evolution through natural selection.

Charles Darwin, born in Shropshire, England, on February 12, 1809, was a naturalist, geologist, and biologist from a family steeped in intellectualism. His father, Robert, was a physician, while his grandfather, Erasmus Darwin, was a prominent thinker during the British Enlightenment. Additionally, his maternal grandfather, Josiah Wedgwood, was the founder of the renowned Wedgwood pottery company. Darwin faced early tragedy with the passing of his mother when he was just eight years old.

In 1825, he began an apprenticeship in medicine under his father before attending the University of Edinburgh. However, he found the lectures dull and became involved with the Plinian Society, a student group focused on natural history. Displeased with his lack of academic diligence, Darwin's father sent him to Christ’s College, Cambridge, to pursue a BA with the aim of becoming a country parson. Even there, Darwin was more captivated by beetle collecting than his studies, yet he managed to perform well in his finals. His reading included works by astronomer John Herschel and scientist Alexander von Humboldt, fueling his aspiration to contribute to natural philosophy by exploring the tropics.

His life took a significant turn when his botany professor, John Stevens Henslow, proposed Darwin as a self-financed naturalist for the HMS Beagle, which would spend two years surveying the South American coast. Initially hesitant, Darwin's father eventually agreed to sponsor the expedition.

The Beagle's voyage commenced in December 1831, lasting five years, during which Darwin studied various animal species in the Galapagos Islands, unearthed fossils, and observed indigenous tribes in South America. He meticulously documented his findings and sent numerous specimens to Cambridge for analysis. One notable observation was the discovery of seashells embedded in volcanic rock cliffs in Cape Verde, and fossilized bones of large extinct mammals alongside seashells in Patagonia.

Aboard the Beagle were three indigenous people from Tierra del Fuego, who had been educated in England as missionaries and were returning to convert their tribe. Although Darwin found them amiable, upon reaching Tierra del Fuego, he noted a stark contrast between them and the local Fuegians, whom he described as living in a state he termed "degraded savages." One of these individuals, Jeremy Button, returned to his previous lifestyle, marrying and showing no inclination to return to England.

Darwin's observations of fossils, geology, and local cultures increasingly led him to believe in a shared ancestry among humans and the notion that no group was inherently superior to another. He also recognized the continuum between humans and animals. After experiencing a significant earthquake in Chile in 1835, he noted changes in the landscape, enhancing his understanding of geological processes.

While he is often celebrated for his observations in the Galapagos, where he spent a mere five weeks, it was here that he noted the variations among finches and tortoises, which contributed to his emerging theory. Unfortunately, he neglected to collect tortoise shells as evidence from the different islands, although he did partake of tortoise meat.

Upon his return in October 1836, Darwin had already gained recognition among scientists, thanks in part to his former tutor Henslow, who had circulated Darwin's geological paper. With his father's financial support, he was able to pursue the role of a gentleman scientist, seeking experts to catalog his extensive collections.

Influenced by Thomas Malthus' Essay on Population, Darwin began writing about species transformation just six months after returning to England, sketching the now-famous branching evolutionary tree labeled "I think."

He drew parallels between farmers selectively breeding livestock and nature's analogous processes, which ultimately led to his theory of evolution via natural selection. However, he spent years conducting research and drafting various scientific papers, particularly focused on his Beagle findings, dedicating eight years to studying barnacles. Thus, for nearly 15 years, his theories on natural selection remained a secondary pursuit, what he referred to as his "prime hobby." Nonetheless, this work allowed him to refine his ideas and bolster his belief in their scientific validity.

Darwin was known for his caution, often fearing ridicule, which caused him to keep his theories concealed while he sought further evidence. He shared them only with botanist Joseph Dalton Hooker in 1844, likening the act to confessing a crime. By July of that year, he had crafted an essay elaborating on his ideas, often discussing them with geologist Charles Lyell.

He began developing his theory in 1837, but it took over two decades to finalize and publish. This delay was precipitated by Lyell informing him about Alfred Russell Wallace, a naturalist who had independently arrived at similar conclusions. Although Wallace may not be as renowned as Darwin, it is vital to acknowledge his contributions as a specimen collector in Indonesia and Borneo.

Upon learning of Wallace's findings, Darwin and Lyell noted their remarkable similarities. Consequently, the theory of evolution was first presented in a joint letter at a meeting of the Linnean Society in 1858, though it initially received little attention. Then, on November 24, 1859, Darwin's comprehensive explanation of his theory was published in his seminal work, On the Origin of Species by Means of Natural Selection, which unexpectedly garnered immense popularity, with initial copies selling out quickly.

Despite fears of controversy, the publication did not provoke as much backlash as anticipated. There was widespread interest, as the concept of evolution had been a topic of discussion since ancient Greece. The Enlightenment and Britain's maritime achievements facilitated new biological discoveries, gradually fostering acceptance among the public and the scientific community.

However, this was a period when the scientific community was closely linked to religious institutions, leading to debates surrounding Darwin's theories. Although he intentionally avoided discussing human origins, hints at such implications incited considerable discourse. He later addressed human ancestry and its connection to other primates in his 1871 work, Descent of Man.

In 1860, a famous debate erupted between Bishop Samuel Wilberforce, known as "Soapy Sam," and Thomas Henry Huxley, nicknamed "Darwin's Bulldog" for his passionate defense of evolution. Wilberforce insinuated that humans descended from monkeys, questioning Huxley about his lineage. Huxley famously retorted that he preferred descent from an ape over a man who misused his intellect.

The crux of Darwin's theory, as articulated in On the Origin of Species, posited that living populations evolve through natural selection across generations. The book suggested that the diversity of life arises from common descent through a branching evolutionary process. Essentially, evolution occurs when natural selection, including sexual selection, leads to certain traits becoming more prevalent or scarce within a population. Darwin explained that individuals best suited to their environments are more likely to survive and reproduce, and if variations are heritable, advantageous traits will spread within the population. Over time, populations that evolve sufficiently distinct traits may become new species. The evidence Darwin gathered during his Beagle voyage and subsequent research formed the foundation of this theory.

Although he grasped the concept of heritability, Darwin lacked knowledge of genetics and could not explain how traits were transmitted. As genetics advanced and the structure of DNA was unveiled in the mid-20th century, evolution emerged as the sole scientific explanation for life's diversity on Earth. With improvements in our understanding of genetics, insights into variability due to mutations, gene flow, and genetic recombination have been integrated into the existing framework. Mechanisms such as natural selection, gene migration, and genetic drift operate on this variability, determining whether traits are inherited or lost.

Darwin's theory has endured rigorous scrutiny and experimentation for over a century and a half, solidifying its status as the central unifying theory in the life sciences, explaining the vast array of life forms on our planet.

It is essential to clarify that Darwin did NOT claim humans descended from monkeys, as implied by Soapy Sam. This misconception has persisted among those unfamiliar with evolutionary theory. Darwin established that all species share common ancestors and that the branching patterns of evolution result from natural selection, where species compete for survival and pass on traits, akin to artificial selection in domestic breeding.

Moreover, he did not initially coin the term "survival of the fittest"; that phrase was popularized by philosopher Herbert Spencer, who applied evolutionary principles to social and ethical contexts. Darwin did utilize the term in the 1869 republication of On the Origin of Species, signifying that nature favors the most well-adapted individuals, not merely the strongest.

In the final decade of his life, Darwin focused on completing his book on earthworms, a subject he had researched intermittently for 40 years. Personally, he married his cousin Emma and they had ten children, two of whom died in infancy, and another, Annie, passed away at ten. His deep devotion to his children is evident in the doodles and sketches they contributed to the draft of On the Origin of Species.

Charles Darwin passed away in 1882 at Down House, his family residence in Kent, and was interred at Westminster Abbey. His remarkable body of work continues to inspire and influence, with over 120 species and nine genera of animals and plants named in his honor.

He concluded On the Origin of Species by Means of Natural Selection with these profound words: “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on, according to the fixed law of gravity, from so simple a beginning, endless forms most beautiful and most wonderful have been, and are being, evolved.”