Its just an intuitive hypothesis. And point to note is that ever since we started doing agriculture, and that was around 20,000 years ago. We started to have mo

Its just an intuitive hypothesis. And point to note is that ever since we started doing agriculture, and that was around 20,000 years ago. We started to have more idle time for creating tools and arts, in general more sedentary than hunting/gathering. Even the works of mathematicians since several centuries ago, I can imagine, would have implied being sedentary while they worked. So software is just the latest in that chain of things since we started doing agriculture.