Ideas about the origin of sedentism and agriculture have been changing in recent years, with a greater emphasis on examining the details of sites case by case. Some new evidence seems to indicate that there was no simple transition or rapid revolution from nomadic subsistence to agriculture and sedentism in the Neolithic. Evidence described from Abu Hureyra, Catal Huyuk, and 'Ain Ghazal suggests that these settlements were not simply either hunting and gathering or farming. In addition, there was probably not a uniform shift at these sites from simple, egalitarian farming villages to large culturally sophisticated settlements. New information supporting these conclusions is given. A discussion is provided concerning whether or not a single factor caused the development of agriculture (which emerged virtually simultaneously throughout the world). Population pressure and climatic change are described as two possible causes. Other workers suggest that evidence from local sites (such as from Abu Hureyra) do not fit these type of general causal models.