A Prime-individual is the smallest measure of individuality where the individual is capable of evolutionary success despite the failure of others in its ecosystem.
Every Prime-individual is composed of Sub-individual Traits that evolve like individuals, but cannot exist on their own. The Sub-individual Trait can either be Dependent, like an eyeball, or Independent, like a shovel. A rock is an object, but a rock forged into an arrowhead and tied to a stick is an Independent Sub-individual Trait. An arrowhead left on the ground for thousands of years is a rock. When that arrowhead is found by an archaeologist and placed on display in a museum, it is still a rock; just a rock that was once an Independent Sub-individual Trait of an ancestor.
Super-individuals can be composed of other Super-individuals, Prime-individuals, and Independent Sub-individual Traits. A country is composed of states, counties, towns and cities, neighborhoods, families (all Super-Individuals), and people (Prime-Individuals). And, at each level, tools and technology (Independent Sub-Individual traits) have become part of the individual.
Evolution is an individual process: only individuals can evolve. And, individuals can only evolve at their level of individuality; either Sub, Prime, or Super. That is, a Prime-Individual cannot become a Super-Individual.