Alfred Russel Wallace: The Forgotten Discoverer.

Greetings. Alfred Russel Wallace (January 8th of 1823 – November 7th of 1913) was an English naturalist, explorer, geographer, anthropologist, biologist and illustrator. 

Wallace independently discovered the theory of evolution through natural selection, with the 1858 publication of his paper on the subject motivating Charles Darwin to set aside the book he was drafting and to quickly write an abstract of it, which was published in 1859 as "On the Origin of Species."

Wallace conducted extensive fieldwork, initially in the basin of South America's Amazon River, subsequently moving his fieldwork to the Malay Archipelago, where he identified the faunal divide now known as the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion which is populated by faunal species of Asian origin, and an eastern portion populated by faunal species that are of Australian origin. Wallace was considered the 19th century's leading expert on the geographical distribution of animal species, and is sometimes called the "Father of Island Biogeography," or more specifically of zoogeography.

Wallace was one of the leading evolutionary thinkers of the 19th century, working on warning coloration in animals and reinforcement (sometimes referred to as the Wallace Effect,) the manner that natural selection contributes to speciation by encouraging the development of barriers against hybridization. Wallace's 1904 book "Man's Place in the Universe" was the first serious attempt by a biologist to consider the possibility of extraterrestrial life on other planets. Wallace was one of the first scientists to write a serious treatise on whether or not the planet Mars harbored life. 

In 1880, Wallace published the book "Island Life" as a sequel to 1876's "The Geographical Distribution of Animals." "Island Life" surveyed the distribution of both animal and plant species on islands. Wallace compartmentalized islands into categories: oceanic islands and two types of continental islands. Oceanic islands, in his view, such as the Galapagos and Hawaiian Islands, called the Sandwich Islands during Wallace's lifetime, formed in mid-ocean and were never part of any continent. Oceanic islands are characterized by a complete lack of terrestrial mammals and amphibians, with their inhabitants (except migratory birds and species introduced by humans) typically the result of accidental colonization and subsequent isolated evolutionary processes. Continental islands, in Wallace's opinion, were divided into those that were recently separated from a continent, like Great Britain, and those separated much less recently, like the island of Madagascar. Wallace discussed how that difference directly affected species of flora and fauna, how isolation affected evolutionary processes, and how that could result in the preservation of classes of animals, such as the lemurs of Madagascar that were remnants of once widespread continental faunas. He extensively discussed how changes of climate, particularly periods of increased glaciation, may have affected the distribution of fauna and flora on various islands. Wallace also addressed the problems of deforestation and the introduction of invasive species. On the impact of European colonization on the island of Saint Helena, he wrote that the island was "now so barren and forbidding that some persons find it difficult to believe that it was once all green and fertile." Wallace explained that the regolith was protected by the island's vegetation, but once the island's plants were destroyed, the soil was washed off the steep slopes by heavy tropical rains, leaving only "bare rock or sterile clay." He attributed the "irreparable destruction" to the feral goats which were introduced by humans in 1513. The island's forests were further damaged by the "reckless waste" of the East India Company from 1651, which used the bark of valuable redwood and ebony trees for tanning, leaving the stripped trees behind to rot and eventually die. "Island Life" was considered an extremely important work at the time of its publication, discussed extensively in scientific circles both in published reviews and in private correspondence.

In the pages of 1904's "Man's Place in the Universe," Wallace concluded that the Earth was the only planet in the Solar System that could possibly support life, primarily because it was the only planetary body on which water could exist as a stable liquid. His treatment of Mars in the book was brief, and by 1907, Wallace had returned to the subject with the book "Is Mars Habitable?," which leveled criticism at the claims made by the American astronomer Percival Lowell that there were Martian canals built by intelligent creatures. Wallace conducted months of dogged research, consulted with various experts, and produced his own scientific analysis of the Martian climate and atmospheric conditions. Wallace pointed out that spectroscopic analysis had shown no signs of water vapor in the Martian atmosphere, that Lowell's analysis of the Martian environmental conditions badly overestimated the average surface temperatures, and that low atmospheric pressures would make liquid water, let alone a planet-girding irrigation system, downright impossible. Wallace became interested in the topic because his own anthropocentric philosophy inclined him to embrace the position that man would be unique in the universe.

Did Charles Darwin alone conceive of the theory of evolution through natural selection? No, for Alfred Russel Wallace accomplished the very same thing at the exact same time as Darwin. Alfred Russel Wallace was truly a magnificent intellect. 

Thank you for your time and consideration.