The watchful eyes of the science-fiction writer Octavia Butler and the composer Julius Eastman looked over the entrance area for the Otolith Group’s exhibition at the Van Abbemuseum. With the larger-than-life images of the show’s two patron saints nearly covering entire walls, it would have been easy to miss the flat glass vitrine on a pedestal containing ten otoliths (tiny calcareous bones found in the inner ear) that had each been taken from a whiting (a cod-like fish). Although the members of the group, Kodwo Eshun and Anjalika Sagar, expressly shied away from billing their exhibition as a