In this article we examine some origins of John Bowlby's attachment theory, a highly influential scientific approach to love and loss in contemporary society. Although some potential influences have been well-documented, others have either received no recognition or have failed to have an impact. We focus specifically on three of Bowlby's predecessors, exploring how these were differentially influential on his work. The first of these, Charles Darwin, was amply endorsed by Bowlby, both in terms of the adaptive background to his theory and more specifically in relation to Darwin's study of the emotions associated with grief. The second, Alexander Shand, was recognized as important but is cited little and omitted from the central issue of the resolution of grief. The third, Bertrand Russell, formulated ideas on attachment and separation before Bowlby, and possibly contributed to the intellectual forces that influenced him too. To our knowledge, Russell's work was not cited by Bowlby, despite the fact that it contained the seeds of many of Bowlby's ideas on attachment. It remains unclear whether this was because he had not read Russell or through omission; there is no definitive evidence either way. Tracing these historical origins illustrates how theory development involves a process of integration and selection, how even radical theories are rooted in previous scholarship, and how it can take decades for inspiring ideas to develop into full-blown, well-tested, theories.