RIP, Muhammad Ali.
Ali died, as you probably know, after a long struggle with Parkinson's.
I for one have generally assumed, when seeing stories about Ali's worsening condition over the years, that there was a direct cause-effect condition between his fights and that disorder.
After all, Parkinson's is a dysfunction of the nervous systems. both of Ali's best-remembered foes in the ring, Foreman and Frazier, were very good at delivering punishment, and the fists of both of those gentlemen had lots of chances to make contact with Ali's skull. How could that not be the prime suspect for subsequent neurological symptoms?
But science conflicts with uninstructed common sense here. To scientists in the pertinent fields, it seems, it is not at all obvious that there was a connection.
Here is Al-Jazeera's take.
BTW, I have just noticed that I have been using both "causality" and "causation" as tags for these posts. So anyone interested in a close examination of Faille's posts on cause-effect relations should probably use both tags rather than either one in order to get a comprehensive view. I'll use both of those labels for this post.