> My layman’s summary of it is that the way genes express themselves is dependent on the surrounding environment so DNA alone doesn’t define how a single cell o

> My layman’s summary of it is that the way genes express themselves is dependent on the surrounding environment so DNA alone doesn’t define how a single cell or larger organism will develop. Epigenetics is the study of how the environment affects gene expression (i.e. turning genes 'on' or 'off'), and it's a relatively new field. https://www.cdc.gov/genomics/disease/epigenetics.htm https://www.cdc.gov/genomics/disease/epigenetics.htm So yes, that's a level of additional complexity, and we're now also learning more about how our microbiome and virome affects our biology as well, which I'm sure will lead to even further complexity... https://en.wikipedia.org/wiki/Human_microbiome https://en.wikipedia.org/wiki/Human_microbiome https://en.wikipedia.org/wiki/Human_virome https://en.wikipedia.org/wiki/Human_virome