I don't know that anyone has written a history on the division of the Africeurasian continent here on /r/AskHistorians in the modern era, but I've written up some background on the ancient division here and here, with an offsite write-up here. Treating Africa as distinct from Eurasia is understandable given how narrow the strip of land connecting them is, so really the problem lies over the division between Europe and Asia.

That division goes back to the Greek ethnographer Hecataeus in the 6th century BCE -- though ancient geographers often put the dividing line at the river Don, in SW Russia, rather than at the Caucasus mountains as is customary today. Like I said, we need someone with expertise in more recent geographic and cartographic history to fill in the more recent history of the division.