William Charles Wells (1757 - 1817) is one of the lesser known figures in early evolutionary thought. But, he occupies an important place as one of three individuals (James Hutton and Patrick Matthew are the other two) to propose a process of natural selection as a mechanism of transmutation before Charles Darwin and Alfred Russel Wallace. Wells was born to Scottish colonists in South Carolina and educated in Scotland. Pro-British sympathies during the American Revolutionary War eventually led him to settle permanently in London where he practiced medicine. Wells published important studies on vision and the formation of dew.
In 1813, Wells wrote a paper (read before the Royal Society) about a white woman with patches of black skin. In this paper (published posthumously in 1818 as "An Account of a Female of the White Race of Mankind, Part of Whose Skin Resembles that of A Negro; with Some Observations on the Causes of the Differences in Colour and Form Between the White and Negro Races of Men"), Wells reflected on racial differences among humans and discussed variation (and local adaptation) in disease resistance between different human races. This led Wells to postulate a basic mechanism of natural selection (he did not use this term) for the divergence of the human races. Charles Darwin was unaware of this essay until it was brought to his attention in 1865 - and it appears to have had little if any effect on the development of evolutionary thought. There are no known extant images of William Charles Wells.
For an excellent treatment of Wells and his ideas on natural selection, please read: Wells, K.D. 1973. William Charles Wells and the Races of Man. Isis 64: 215 - 225. pdf here