There are variants of the joke for both spherical cows and chickens going back decades. > "Postulate a spherical chicken ...", as presented in a 1973 letter t

There are variants of the joke for both spherical cows and chickens going back decades. > "Postulate a spherical chicken ...", as presented in a 1973 letter to the editor of the journal Science titled A Spherical Chicken. Turing discussed spherical horses even earlier :).