Will Smith was asked to serve as one of the pallbearers at Muhammad Ali’s funeral Friday. Smith and Ali became close when the former portrayed the boxer in the 2001 biopic, Ali. It’d be worth asking if he was thinking of Ali when he made his most recent picture, Concussion, playing Bennet Omalu, the Nigerian doctor who fights the NFL over his research into chronic head injury and brain deterioration. It seems that most accounts of Ali’s life, positive and negative, are skirting the rather obvious issue: The Parkinson’s Disease he was diagnosed with in 1984 is almost certainly attributable in part to what made him for a while the most famous man in the world.

“Muhammad Ali’s Parkinson’s may not have been caused by boxing” is the counterintuitive title of one article. Okay, maybe we’ll never be 100 percent sure, even if the Ali family does ask for an autopsy. (They’re not leaning in that direction now.) But lots of medical professionals say they know “that boxing could lead to Parkinson’s disease.”