About two and a half hours northeast of New York City, atop a mountain in the Berkshires, lies Jacob’s Pillow. And on the grounds of this rustic family farm turned international dance festival, in an 18th-century barn gifted from a Hollywood dancer, hang over seventy photographs. In one, Black American modern dancer and choreographer Alvin Ailey sways back into a jazzy hinge. A few feet away, German neo-expressionist dancer and choreographer Pina Bausch boldly peaks up at her partner. Across the room...