Ember existed before backbone.js by about 2-3 years under the name sproutcore.
Backbone.js's first release was in 2010.
Backbone.js was the starting point of the huge JS MVC community that exists today. Primarily due to it's simplicity and Rails-esque nature, where as Sproutcore was unwieldily and enterprise-software-esque until work on Ember started.
Rails had many early predecessors as well but Rails was the one that did it right, and spurred that style of framework's popularity.
Sorry for the earlier "well, actually." :)