Making UFC brawlers seem decidedly dainty by comparison, Ireland’s Quinn McDonagh clan has for decades engaged in bare-knuckle brawls with rival families on remote country roads and abandoned asphalt lots. Ian Palmer’s documentary Knuckle details this astonishingly primal tradition through the prism of Quinn McDonagh hero James, who defends ancestral honor (and earns cash) by beating the pulp out of adversaries in bouts that can last as long as two brutal, bloody hours. The war dates back to some early-1990s murders that, 20-odd years later, seem a mere pretext for providing these bruisers with an outlet for deeply rooted hostility. Palmer’s grainy, handheld camerawork won’t win any aesthetic prizes, but it’s in tune with his subject. James’s increasingly conflicted feelings regarding these battles provide an added measure of emotional complexity, while more rending still is the sight of young children witnessing their elders pounding each other to no significant end—striking images that encapsulate the film’s portrait of hate as inheritance.