To an outsider like your humble scribe, the U.S.’s most heavily marketed sport seems a Hobbesian parable — play on the field is nasty, brutish and comically short. Rugby offers a similar dynamic of head-on aggression but lacks the heavy padding and equipment that armor American football and inevitably lead to terrifying concussions. The number of recent incidents of ex-players’ dying of mysterious brain injuries ought to have raised enough alarm.