"PHILOSOPHICALLY SPEAKING...":

My high school "Philosophically Speaking" class discussed the issue of identity this week (e.g., am I my mind? or my body? or both? and how does our answer to this question shift depending on the situation?) A UPenn biologist and philosopher of science throws in another complication: am I just the cells that carry my DNA? or am I the collective of organisms that live within my body and without whom I couldn't survive?

"You yourself are swarming with bacteria, archaea, protists and viruses, and might even be carrying larger organisms such as worms and fungi as well. So are you a holobiont, or are you just part of one? Are you a multispecies entity, made up of some human bits and some microbial bits – or are you just the human bits, with an admittedly fuzzy boundary between yourself and your tiny companions? ... On this view, the ecological notion of holobiont (the host and all its resident microbes) is given additional properties. It’s an entity that’s coherent enough to have its own hologenome, made up of the host genome plus all the microbial genomes. A major implication of this theory is that natural selection doesn’t just act on the genome of individual organisms: it acts on the hologenome of holobionts, which are seen as single units that can evolve at the level of the holobiont. Today, researchers engage in fierce debate over which forces shape holobionts and host-microbiome systems. They can be roughly split into two factions, the ecological and the evolutionary. On the ecological side, holobionts are seen as complex and dynamic ecosystems, in constant flux shaped by individual interactions from the bottom up. So you are part of a holobiont. But this stands in opposition to the evolutionary account, which casts holobionts as higher-level entities akin to organisms or units of selection, and believes that they are shaped as a whole from the top down. On this view, you are a holobiont."
aeon.co/ideas/i-holobiont-are-you-and-your-microbes-a-community-or-a-single-entity