...the survival of a species depends on adaptation and learning on six distinct timescales. On the shortest, most immediate scale, species must exist from year to year. The unit of survival for this year-to-year existence is the individual life form. Over decades, the unit of survival is the family, whose multiple generations last much longer than any single individual's life span. Over centuries, it's the tribe or nation. Over millennia, it is an entire culture. Over tens of millennia, it is the species itself, slowly evolving or surrendering to an evolved competitor. And over eons, the unit of survival is 'the whole web of life of our planet.' Human beings have endured as a result of our ability to adapt on all six scales of being and to balance the conflicting demands of each.