Wells fue el mayor de tres médicos británicos que expresaron teorías evolucionistas entre 1813 y 1819. Los otros fueron James Cowles Prichard y William Lawrence.

En 1813, un artículo de Wells fue leído en la Royal Society y publicado en 1818. Se trató de Two Essays... with some observations on the causes of the differences of colour and form between the white and negro races of men. By the Late W.C. Wells…with a Memoir of his life, written by himself. El objetivo era tratar de explicar cómo surgieron las razas humanas.^[3]​^[4]​^[5]​ Luego de algunas reflexiones preliminares en torno a las razas humanas y a la domesticación de animales, expresó:

What was done for animals artificially] seems to be done with equal efficiency, though more slowly, by nature, in the formation of varieties of mankind, fitted for the country which they inhabit. Of the accidental varieties of man, which would occur among the first scattered inhabitants, some one would be better fitted than the others to bear the diseases of the country. This race would multiply while the others would decrease, and as the darkest would be the best fitted for the [African] climate, at length [they would] become the most prevalent, if not the only race.

Two essays: upon a single vision with two eyes, the other on dew (1818), Wells W.C.^[6]​

Charles Darwin y Alfred Russel Wallace no tuvieron noticia de este trabajo cuando publicaron sus teorías en 1858, pero más tarde Darwin aceptó:

In this paper he [Wells] distinctly recognizes the principle of natural selection, and this is the first recognition which has been indicated; but he applies it only to man, and to certain characters alone. After remarking that negroes and mulattoes enjoy an immunity from certain tropical diseases, he observes, firstly, that all animals tend to vary in some degree, and, secondly, that agriculturalists improve their domesticated animals by selection; and then he adds, but what is done in this latter case by art, seems to be done with equal efficacy, though more slowly, in the formation of varieties of mankind, fitted for the country which they inhabit.

The origin of species by means of natural selection (1886), Charles Darwin^[7]​

Por lo tanto, el crédito por la formulación de la hipótesis de la selección natural debe atribuirse a Wells más que a Edward Blyth o a Patrick Matthew. Pero esta formulación tenía un alcance muy restringido comparada con las teorías de Darwin y Wallace.

•   Wikisource contiene obras originales de o sobre William Charles Wells.

• Wells W.C. 1814. An essay on dew. Taylor & Hessay, London.
• Wells W.C. 1818. Two essays: upon a single vision with two eyes, the other on dew. Constable, London. Esta obra contiene el apéndice titulado 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 cause of the differences in colour and form between the white and negro races of man. En este apéndice aparece la hipótesis de la selección natural. - Electronic copy
• Wells W.C.. 1811-1812. Transactions of a Society for the Promotion of Medical and Chirurgical Knowledge con los siguientes estudios:

• Observations on Erysipelas.
• An instance of an entire want of hair in the human body.
• Observations on the dropsy which succeeds Scarlet Fever.
• A case of Tetanus, with observations on the disease.
• A case of aneurism of the Aorta, communicating with the Pulmonary artery.
• A case of considerable enlargement of the Cœcum and Colon.
• A case of extensive Gangrene of the cellular nembrane between the muscles and skin of the neck and chest.
• On rheumatism of the heart.
• On the presence of the red matter and serum of the blood in the urine of dropsy, which has not originated in Scarlet Fever.
• Observations on Pulmonary Consumption and intermittent fever, chiefly as diseases opposed to each other; with an attempt to arrange several other diseases, according to the alliance or opposition which exists between them, and one or other of the two former.

• Munk's Roll of the Royal College of Physicians
• Dictionary of National Biography
• James R.R. William Charles Wells. British Journal of Ophthalmology, November 1928.