> Too lazy to move is more likely. Conditions that made it favorable to
> stay in one place for a while eventually ended, but at that point we had
> already set down roots and weren't too keen on going back to a nomadic
> lifestyle.

Apparently, this is the case with the Natufians, considered one of the
first agricultural groups. They were a settled hunter-gatherer society,
living in permanent villages. Climate changes took away their steady food
supply, and they had to do something. A splinter group tried to go back to
nomadic ways, and did not survive. The main group "converted" to
agriculture very rapidly (a couple centuries), and did not look back. It
was truly a revolution in the strict sense of the word.

However, it's not hard to imagine that prior to this they were
experimenting with gardening. Some nomadic Native American cultures were
known to plant maize, beans, etc. in various places during their journeys,
harvesting upon their return. A more settled society could easily use
casual gardening to supplement their gathering efforts. So, the step from
"paleo gardening" to full-scale agriculture is not quite as big a leap as
some might think.