He was born in The Pleasance, in south-east Edinburgh in 1740, the son of Jean Robertson and Alexander Smellie, architect and master builder.

[1] During this time he was promoted to the subeditorial position corrector of the press, and won his employers the Edinburgh Philosophical Society's prize for the most accurately printed edition of a Latin text.

It was a masterful composition although, by Smellie's own admission,[4] he borrowed liberally from many authors of his day, such as Voltaire, Benjamin Franklin, Alexander Pope and Samuel Johnson.

[5] Nevertheless, the first edition of the Britannica contained gross inaccuracies and fanciful speculations; for example, it states that excess use of tobacco could cause neurodegeneration, "drying up the brain to a little black lump consisting of mere membranes".

The practice of this useful art has been hitherto almost entirely confined to a set of men who are totally ignorant of anatomy, and the general principles of medicine.

[12][13] Smellie is also noted for his English translation of the famous Histoire Naturelle of the French naturalist Georges-Louis Leclerc, Comte de Buffon.

In 1779, Smellie was nominated to be the University of Edinburgh's professor of natural history; however, the post was awarded to Dr John Walker, allegedly due to politics.

Smellie continued to publish a wide variety of works, including his two-volume Philosophy of Natural History, which became a set text at Harvard University in the 19th century, and at least two of the four-volume set of Thesaurus medicus: sive, disputationum, in Academia Edinensi, ad rem medicam pertinentium, a collegio instituto ad hoc usque tempus, delectu which reprinted Edinburgh medical theses of the 18th century.