The theory of evolution by natural selection is most often associated with Charles Darwin. However, Alfred Russel Wallace independently conceived a nearly identical theory. This highlights how scientific ideas can emerge simultaneously from different minds observing similar patterns in nature.
Alfred Russel Wallace’s Independent Discovery
Alfred Russel Wallace embarked on extensive scientific expeditions, first to the Amazon River basin (1848-1852). He collected numerous specimens and observed species distribution, shaping his thoughts on biological change over time.
His most significant work occurred during an eight-year journey through the Malay Archipelago, from 1854 to 1862. Wallace meticulously studied the region’s rich biodiversity, noting distinct differences in animal species on islands separated by narrow straits, now known as the “Wallace Line.” He collected over 125,000 specimens, including more than 5,000 previously unknown species.
While on Ternate in February 1858, Wallace experienced an insight while suffering from malaria. He recalled Thomas Malthus’s essay on population, which described how populations outgrow their food supply, leading to a struggle for existence. This concept, combined with his observations of variation within species and adaptation, led him to formulate the principle of natural selection.
Wallace quickly wrote an essay detailing his theory, titled “On the Tendency of Varieties to Depart Indefinitely from the Original Type.” He sent this manuscript to Charles Darwin, requesting Darwin’s opinion and assistance in getting it published.
The Parallel Theories and Joint Presentation
Wallace’s essay, which arrived in June 1858, presented a theory of evolution by natural selection that strikingly paralleled Darwin’s unpublished work. Both men posited that individuals with advantageous traits are more likely to survive and reproduce, passing those traits to their offspring. This process leads to the gradual accumulation of beneficial adaptations and the emergence of new species.
Darwin was deeply unsettled by Wallace’s manuscript, as it encapsulated decades of his own research. He recognized the similarities between Wallace’s ideas and his own unpublished theory of natural selection. Faced with this independent discovery, Darwin turned to his colleagues, Charles Lyell and Joseph Hooker, for advice.
Lyell and Hooker, aware of Darwin’s long-standing work on evolution, recognized the importance of acknowledging both scientists’ contributions. They arranged for Wallace’s essay to be presented alongside excerpts from Darwin’s unpublished writings and a letter outlining his own theory. This joint presentation occurred at the Linnean Society of London on July 1, 1858.
The papers read at this meeting included Wallace’s full essay and two of Darwin’s pieces: an abstract of his 1844 essay on species and a letter to Asa Gray from 1857. This simultaneous presentation ensured that both men received credit for their independent discoveries of natural selection. The core mechanism involved environmental pressures acting on heritable variations, leading to differential survival.
The Legacy of a Shared Idea
The joint presentation at the Linnean Society had a profound effect on the dissemination of evolutionary theory. It served as a catalyst for Charles Darwin, prompting him to accelerate the publication of his comprehensive work. In November 1859, Darwin published On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. This influential book provided extensive evidence and arguments for natural selection, building upon the joint presentation.
Alfred Russel Wallace continued his scientific work, making significant contributions to biogeography and evolutionary biology. He is remembered not only for his independent discovery of natural selection but also for his later work on island biogeography and his advocacy for human impact on the environment. Wallace’s collaboration with Darwin cemented his place in the history of science as a co-discoverer of one of biology’s fundamental principles.