Virology Lectures 2020 #1: What is a Virus?

At the theorized beginnings of life, this lecture leads me to think that, perhaps it was a virus that allowed or caused the first single cell organisms to begin joining together to begin the process of building more complex organisms. (more below)

When free floating DNA came to code for cell walls, the only thing these cells would be interested in admitting would be food.  They would hardly be seeking foreign DNA to add to their code, so they'd have a very long road to accessing any sort of symbiotic relationship.  Mainly because the water would be so full of food/chemicals/etc., symbiotic relations would hardly be an advantage of any sort.  Rapidly mutating viruses, however, could change that rather quickly (in just a short few millions of years).  I'd envision that the union of cells into multicellular organisms at first, did not result in any survival advantage, since there was not yet predation which would come much later because it is a much more complex mode of existence.  A virus solution would force unions between cells without the need of an evolutionary motive.