The present day abstract that accompanies a scientific paper is a relatively new concept. Since the beginning of expository writing, there have been attempts to pull things together at the end, but there has been no standard. In the heyday of German medicine in the last century, the Zusammenfassung ("seizing together") came into being, but it was variable in length and content in conformance with the whim of the writer.
The following advice given by Sir Clifford Allbutt, as recently as 1923, shows the expressed need for such a summary in certain articles.
On the completion of a long thesis, or important scientific essay, it is well to draw up a syllabus of the argument and to place it at the beginning: in any case let the conclusions be set out succinctly at the end: it is not for the author to compel the reader to peruse his essay.1
WARREN R. The Abstract. Arch Surg. 1976;111(6):635-636. doi:10.1001/archsurg.1976.01360240015001