Best known for his papers on the topic of evolution, this award-winning, 19th-century naturalist independently developed the idea of natural selection around the same time that Charles Darwin became famous for formulating the important theory.
In his late teens and early twenties, he worked as an apprentice to his surveyor brother, William. He later taught cartography classes at a school in Leicester, England.
He formulated the "Wallace effect" hypothesis, which laid out the idea that natural selection protects against the hybridization of animal species. Also an expert on biogeography (the study of the distribution of different species), he traveled widely and conducted research in both the Malay Archipelago and the Amazon River basin.
His marriage to Annie Mitten resulted in a daughter named Violet and sons named Herbert and William.
He defended Charles Darwin's On the Origin of Species against the attacks of numerous late 19th-century critics.