Everyone knows that Charles Darwin discovered evolution, but he wasn’t the only fish in the evolutionary pond. Alfred Russel Wallace isn’t widely known as such, but he ‘discovered’ evolution too, and in fact his independently-proposed theories on evolution prompted Darwin to publish his own at a time when the latter had been somewhat hesitant to do so.
Early Life and Work
Alfred Russel Wallace was born in January of 1823, in Monmouthshire, Wales. His family moved to Hertford, near London, when he was five, and upon reaching adulthood he trained as a surveyor with his brother William.
During his early twenties Wallace befriended Henry Bates, a notable entomologist, began collecting insects, and also began reading evolutionary works, including Charles Darwin’s Journal and Remarks, concerning the latter’s voyages aboard the Beagle. Wallace was inspired by what he read, and decided to begin traveling as a naturalist.
Wallace embarked upon his first voyage in 1848, bound for Brazil, where he hoped to collect insects for sale, and find evidence of the transmutation of species (this being the term commonly used at the time to describe the process whereby one species evolved into another). Wallace spent four years abroad before returning to England, where he published several scientific papers and books, and began interacting with other naturalists, including Darwin.
Between 1954 and 1862, Wallace journeyed in the Malay Archipelago (now Malaysia and Indonesia), studying the fauna and flora and collecting specimens for sale. During these years, he collected more than 125,000 different specimens, including 1,000 which were entirely new.
Evolutionary Journeys and Theories
Having embarked on his travels already in possession of a belief in the transmutation of species, Wallace planned field work which would test related theories. One of these—that closely-related species would inhabit the same or neighboring territory if evolution were a valid concept—he took extensive notes on, and he also noted that in cases where territories were separated by geographical barriers, there was a resulting separation in the relatedness of species.
Wallace’s work in the Malay Archipelago convinced him once and for all that evolution was fact and not theory, but as yet there was no evidence one way or the other as to how the process actually occurred.
According to Wallace’s autobiography, it was while he lay in bed with a fever that he came up with the concept of natural selection. In the work, he describes having thought about the fact that animals procreate so quickly that the rate of destruction must be enormous to prevent overcrowding. Having thought about this he then wondered how it was that some animals died, while others lived – and considering that, he realized that it was the “best fitted" that survived.
Early in 1957, Wallace and Darwin began discussing their theories, with Darwin noting that the two naturalists were thinking alike in evolutionary terms. Together, the two men presented a short series of papers to the Linnean Society in July of 1958. Wallace presented a paper entitled On the Tendency of Varieties to Depart Indefinitely from the Original Type while Darwin presented an Extract from an Unpublished Work on Species. Around eighteen months after this presentation, Darwin published On the Origin of Species, from which the extract had been taken.
Wallace’s Contributions to Evolution
Wallace made some particular contributions to evolutionary science which deserve special mention.
During 1867, Darwin mentioned to Wallace that he was having a problem with a particular aspect of the selection process, namely that some caterpillars evolved a color scheme which made them highly conspicuous. In response, Wallace noted that many of the most conspicuously colored butterflies he had come across tasted and smelled strangely, and that it seemed likely that the color scheme was a warning to predators. Over time the predators had come to associated the colors with unpleasant taste or smell, and stopped using those caterpillars as a food source.
This concept of warning coloration was just one of several contributions which Wallace made in the field of animal coloration, and was in fact a consistent point of contention between Wallace and Darwin, as the latter believed variation in coloration was generally attributable to sexual selection.
In 1889, Wallace wrote and published Darwinism, in which he defended On the Origin of Species and the concept of natural selection. In this book he proposed what would later become known as the Wallace Effect: that natural selection could drive reproductive isolation of two diverging species, by encouraging the development of barriers which would prevent mating between the two.
Wallace theorized that at a certain point of divergence, those barriers would produce conditions in which hybrids of the two species would be significantly less fit than either of its parent forms, thus providing an evolutionary barrier against inter-species mating. These theories have been given validity in modern evolutionary science by empirical data as well as by mathematical models.
Wallace and Spiritualism
Despite having previously rubbished spiritualist concepts, Wallace began investigating spiritual phenomena in 1865, and came to believe that some of the phenomena he witnessed at séances had basis in reality.
Unfortunately, Wallace’s growing interest in spiritualism led to significantly strained relationships between him and the rest of the scientific community. Wallace came to believe that while the body was subject to evolutionary forces, it was impossible that something as infinitely complex as the human mind was subject to the same forces.His frequent and public statement of these beliefs unfortunately caused significant damage to his scientific reputation, even with formerly close colleagues such as Darwin himself.
This may, sadly, be one of the reasons why Wallace’s fame as a natural scientist dissipated so quickly after his death in November 1913. Rarely is Wallace known as a proponent and scientist of evolution, despite the enormous contributions he made to the study of the science.