Wallace, Alfred Russel (1823-1913), British naturalist, collector of wildlife specimens, and author who was one of the first to formulate the groundbreaking theory of evolution by natural selection. Wallace's theory was made public at the same time as that of Charles Robert Darwin. Wallace and Darwin worked independently, each unaware of the other's research. Yet both developed the same insight into the biological mechanism by which species gradually change by adapting to the particular pressures and requirements of their environment. At a time when most people believed that species were the fixed and unchanging product of divine creation, this theory was revolutionary.
Born in the small village of Usk, Wales, Wallace received his only formal education in the one-room Hertford Grammar School. Leaving school at age 14, Wallace joined his brother in London and began to train as a surveyor. He also embarked on an extensive program of self-education, attending lectures and night classes, reading books about geology, optics, mathematics, botany, and other subjects. He developed a keen interest in wildlife and began collecting beetles. In 1849 he set off for the Amazon River with the British naturalist Henry Walter Bates, convinced that he could make a living collecting exotic specimens of wildlife for museums and universities.
Wallace spent three years deep in the Amazon basin, collecting many species of fish, insect, and plant life. He returned to England with these specimens, establishing a reputation as a first-rate wildlife collector. He set out again in 1854 on an eight-year trip to what was then known as the Malay Archipelago—today, Indonesia and Malaysia. On a journey that covered some 23,000 km (14,000 mi), Wallace collected nearly 125,000 specimens of mammals, insects, shells, and reptiles. He also made careful observations of species and how they varied. In particular, he noted that different species separated by some geographical boundary, such as a river, were in many instances very similar to one another.
While in Malaysia, Wallace began to formulate his theory of natural selection, the idea that competition for survival in a local environment exerts pressure on populations to adapt. In effect, nature selects the individuals with the best combinations of traits for survival. As these individuals pass their traits on to their offspring, the number of individuals with this trait increases. Those individuals lacking the beneficial traits gradually die off. As natural selection works on a population that is adapting to a new environment, the population may undergo such sufficient change that, in some cases, it will become a distinct and separate species from its parent species.
In 1858, while still on his Malaysian journey, Wallace wrote a paper describing his theory and sent it to Darwin. Wallace was unaware that Darwin had been developing the same theory for nearly two decades—although Darwin had not yet published it. Admirably, Darwin elected to share credit with the younger naturalist. He arranged to have Wallace's paper and some of his own unpublished writings read together at a scientific meeting of the Linnean Society in London in June of 1858. The next year, Darwin published On the Origin of Species, the book that made the theory of natural selection famous.
Upon his return to England, Wallace supported himself primarily as a writer and lecturer. His written works include The Malay Archipelago (1869), Geographical Distribution of Animals (1876), Darwinism (1889), and Man’s Place in the Universe (1903). Later in life Wallace became head of the Entomological Society and president of the British Association, a scientific organization. His other distinctions included the Darwin Medal of the Royal Society (1890), the Copley Medal of the Royal Society (1908), and the Order of Merit (1908).
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