Saffo's work demonstrates only that molgulids can live and reproduce without Nephromyces in the laboratory. In nature, I've never seen any adult, reproductive molgulids without their symbionts. At some point in the past, it seems apparent to Saffo that the ancestors of these organisms lived independently. The symbiotic relationship developed over time. By identifying the unique relationship, Saffo confirmed some popular ideas about eukaryotic cells.
Eukaryotic cells are cells which have a nucleus and contain internal structures called organelles.
Most cells in the human body are of this type. One of those ideas is that eukaryotic cells originated when one type of single-celled organism was engulfed by another. Instead of being digested or destroyed, both organisms combined and began to work together as one. For example, mitochondria are organelles that function as the chemical engines of individual cells. Most scientists believe that they once were independent organisms.