On Religion as the Glue: Science says

Civilization has its basis in religion – springs from religion - is a Baha’i view.-gw

Religion could also stabilise large human societies, otherwise destined for collapse. Because 200,000 years of human history was dominated by small hunter-gatherer societies, some researchers argue that human groups have a built-in limit of about 150 people, before fissioning or collapsing.

Religion could be the glue that keeps members of larger groups from turning on each other or freeloading. An analysis of 186 societies found that cultures with large populations tend to subscribe to religions that enforce human morality.

http://www.newscientist.com/blogs/shortsharpscience/2008/10/does-religion-make-people-gene.html?DCMP=ILC-rhts&nsref=ts12_pic