Buss and Greiling cite individual differences in attachment as a principal illustration of adaptive individual differences. This particular example, however, is a highly controversial one: Many if not most relationship researchers assume (implicitly or explicitly) that insecure attachment patterns reflect some kind of malfunction of the attachment system in modern environments rather than evolved facultative strategies. I therefore review some of the arguments and evidence on both sides of this issue, along with the closely related topics of mating/reproductive strategies and parental investment. In the end I support the Buss-Greiling position, but for reasons not discussed in their article.