Symbiosis is the prolonged physical association of two or more different kinds of organisms. Endosymbiosis involves one life-form actually living inside another, often in a long-lasting merger. Symbiogenesis, the source of true evolutionary novelty, occurs when the mergers of independent organisms actually form composites. A totally new kind of being may then evolve.
All life forms—with the exception of bacteria from which they evolved—are consortia. Our cells are the result of millions of years of mergers, the outcome of once free-living bacteria that came together in permanent relationships.
We are all chimera, composites of many life-forms and many mergers. Identity is less an object than a process. We all envelop traces of bygone beings.