It has been generally accepted that the macromolecular hypothesis was for the first time presented by H. Staudinger (1920.). It is shown in this article, however, that Roger Boscovich, in his monumental work Theory of natural philosophy, pointed out, as early as the 18th century that the spiral atomic chains could be formed. He also pointed out that the shape of the chain could be considerably changed due to slight changes of the distances between atoms, as well as that these sequences of atoms have elastic properties. The author of this article also presented some examples of the applications of Boscovich's theory to the interpretation of free-radical polymerization of compressed ethylene gas and liquid methyl methacrylate. The priority of Boscovich's macromolecular hypothesis is unquestionable and his theory is still applicable in the current polymer science.