One important point in the history was the release of the V8 engine. It introduced the Event Loop, which allowed for asynchronous Callbacks using the WebApis of the browser. (For example for making Ajax Requests).
But to my knowledge AJAX is quite a bit older then V8, and it was used for making HTTP Requests on the client and updating a webpage asynchronously. So my question is: was asynchronous programming possible before V8? If yes, how was it done and why is V8 considered the beginning of asynchronous programing? If no, was there absolutely no asynchronous code possible before and what was AJAX used for?