Well to be sure accumulation of assets was a big deal, but there are people who posit other, not necessarily mutually exclusive, reasons that farming societies invented the concept of chastity outside of marriage. One compelling argument is that they used it as a form of birth control.
From what evidence we have we can see that starvation was relatively rare in hunter-gather societies, but it was really common in farming communities, especially when there were more mouths to feed than the land could support. The lords needed some way to make sure that the population couldn't rise above what the land was able to support, so they used marriage, especially church-sanctioned marriage, as a way to control the peasant population. According to Dr. Wyman
only 40% of people in medieval Europe were married(Sorry for the zip, lecture #9 is the one that lists this info if you are interested, fascinating course overall). The landlords simply controlled the church who in turn controlled marriage. Civilizations have been using marriage, and the taboos of sex outside marriage, to control population for eons.