Suicide is widespread amongst humans, unique to our species, but difficult to reconcile with natural selection. This paper links the evolutionary origins of suicide to the archaic, but once widespread, practice of human sacrifice, which like suicide, was also unique to humans, and difficult to reconcile with natural selection. It considers potential explanations for the origins of human sacrifice, particularly René Girard's mimetic theory. This states that the emergence in humans of mimetic (imitation) traits which enhanced cooperation would also have undermined social hierarchies, and therefore an additional method of curtailing conspecific conflict must have emerged contemporaneously with the emergence of our cooperative traits. Girard proposed the scapegoat mechanism, whereby group unity was spontaneously restored by the unanimous blaming and killing of single victims, with subsequent crises defused and social cohesion maintained by the ritualistic repetition of such killings. Thus, rather than homicide being the product of religion, he claimed that religion was the product of homicide. This paper proposes that suicidality is the modern expression of traits which emerged in the ancestral environment of evolutionary adaptedness as a willingness on the part of some individuals, in certain circumstances, to be sacrificial victims, thereby being adaptive by facilitating ritualistic killings, reinforcing religious paradigms, and inhibiting the outbreak of more lethal conflicts. Using Hamilton's rule of inclusive fitness, it is argued that risk factors for suicide can be understood in terms of victim selection and social circumstances, which would have maximised inclusive fitness. [ABSTRACT FROM AUTHOR]