Humans are a remarkably successful species. We have colonized virtually every terrestrial habitat on Earth, in numbers that by far exceed what would be expected for a mammal of our size. We exhibit behavioral diversity that is unparalleled in the animal kingdom, in spite of comparatively low genetic diversity. And we have resolved countless ecological, social, and technological challenges, from splitting the atom to irrigating the deserts. These achievements are widely attributed to our species' unique capability for cumulative culture ‒ the extensive accumulation of knowledge, and iterative improvements in technology, over time. Yet in spite being so central to our own success, cumulative culture is exceptionally rare in nature: indeed, it is not clear that any other living species possesses it. This project ‒ a unique interdisciplinary collaboration between biologists and psychologists at the University of St Andrews ‒ sets out to understand this paradox. It comprises a series of interlocking experimental and theoretical projects designed to investigate the evolution of the human capabilities for complex cumulative culture, creativity, and trust from a comparative perspective.