This type of redefining the self does indeed have major implications for arts and humanities as well as science.
Psychology has long been on the border of Arts and Humanities and Science. Psychologists have long dealt with the fact that we are much more than our genetics. Genetics may well set limits but developmental environment, culture, the interaction between the way we look and the way society treats us etc etc.
But microbiome research does indeed add yet another layer of complexity. Incorporating these new insights into what goes into being a human into aspects of arts and humanities, including law, will be an interesting development to follow... I look forward to this integration...should add more awareness to how we do and can influence others and vice versa.