"...a historical causal explanation..."

From Foucault:  A Very Short Introduction by Gary Gutting.  Oxford University Press.

Page 47:  "The forces that drive our history do not so much operate on our thoughts, our social institutions, or even our environment as on our individual bodies.  So, for example, punishment in the 18thC is a matter of violent assaults on the body:  branding, dismemberment, execution, whereas in the 19thC it takes the apparently gentler but equally physical form of incarceration, ordered assemblies, and forced labour.  Prisoners are subjected to a highly structured regimen designed to produce 'docile bodies'.  A Foucaultian genealogy, then is a historical causal explanation that is material, multiple, and corporeal."

This aligns with the observation that there does not have to be a straight line from a single event/action/thought/process in the past to a given outcome in the present.  Thoughts and institutions, etc., are not omitted among the "forces that drive our history" but the actions on the body are more powerful in cementing those forces and the continued shaping of thoughts, social institutions, and the environment.

This operates outside of the example of crime and punishment.  Application:  schools and codes of conduct. 

• The students are given a dress code that includes not only dress but a checklist for physical appearance (i.e., visible tattoos and piercings) that operates on the individual body
• Observations and classifications are made about 'socially appropriate dress' and corresponding judgements (operates on thoughts)
• Becomes part of the culture of the institution and, ultimately, the 'environment' of that institution​
• Continued action on the body (dress, personal appearance) creates a visual that encourages compliance, makes the 'offender' stand out, and serves as a visual reminder of what is not acceptable; disciplinary action (stopping the student in the halls, questioning) serves as a caution to others to encourage continued compliance.

​What is the problem that requires a genealogy?  Particular students are disproportionately affected by the school's code of conduct and government policy.