Alfred Russel Wallace
Alfred Russel Wallace, OM
Order of Merit
The Order of Merit is a British dynastic order recognising distinguished service in the armed forces, science, art, literature, or for the promotion of culture...

, FRS (8 January 1823 – 7 November 1913) was a British naturalist
Natural history
Natural history is the scientific research of plants or animals, leaning more towards observational rather than experimental methods of study, and encompasses more research published in magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study...

, explorer, geographer, anthropologist and biologist. He is best known for independently proposing a theory of evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 due to natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 that prompted Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

 to publish his own theory.

Wallace did extensive fieldwork, first in the Amazon River
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

 basin and then in the Malay Archipelago
Malay Archipelago
The Malay Archipelago refers to the archipelago between mainland Southeastern Asia and Australia. The name was derived from the anachronistic concept of a Malay race....

, where he identified the Wallace Line
Wallace Line
The Wallace Line separates the ecozones of Asia and Wallacea, a transitional zone between Asia and Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origin is present...

 that divides the Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

n archipelago into two distinct parts, one in which animals closely related to those of Australia are common, and one in which the species are largely of Asian origin.

I think I have fairly heard and fairly weighed the evidence on both sides, and I remain an utter disbeliever in almost all that you consider the most sacred truths [...] I can see much to admire in all religions [...] But whether there be a God and whatever be His nature; whether we have an immortal soul or not, or whatever may be our state after death, I can have no fear of having to suffer for the study of nature and the search for truth.

Letter to a relative, 1861