[zkmon]

The phrase "survived on a knife edge" or the dramatization is a product of awareness of modern living. For them at those times, neither "survival" nor "struggle" has any meaning. There was likely no consciousness of such concepts. They just continued via instincts and evolutionary goals such as reproduction, food gathering, hunting etc, which were just the same activities their ancestors did, with no changes. Lack of change should actually mean pretty normal life, instead of rapid change-related struggle that we go through now.

[vasco]

We are also surviving on a knife edge from the perspective of a super advanced civilization that doesn't deal with disease or has more energy than they know what to do with. Everything is relative

[PowerElectronix]

Funily enough, that could describe pretty well the first sapiens that learned how to make fire.

[jojobas]

Hunter-gatherers were always on a knife edge, as they were in equilibrium with the food supply. Killing children in dry years, constant fighting over resources, massacres of entire tribes. Of course they didn't know they were on the knife edge, so what?

[zkmon]

Relative terms such as "living on edge" require normative references. It was just business-as-usual, normal life for them, in their own normative reference frame. Just like how cultures in some parts of the world today see things as normal, which would be abnormal to others. It's all your reference frame. There is no permanent or universal norms that can tell what is normal.