Adaptive software development processes were introduced as early as 1974 as a new way to develop software. These were called "lightweight" models but they never dominated the software industry. But it wasn't until the mid-1990s, that agile software development started to be considered as a replacement to mainstream "heavyweight" models traditionally aligned under the Waterfall model, and considerable time, money and effort taken to further develop "lightweight" models/processes.

These new models or processes such as Scrum (1995), Crystal Clear, Extreme Programming (1996), Adaptive Software Development, Feature Driven Development, and Dynamic Systems Development Method (DSDM) (1995) have recently (2001) been brought under the Agile Methodologies umbrella and an effort undertaken by 17 leading figures in the field of agile software development to codify these principles under the "Agile Manifesto".