Religion has been intensely studied in the last years inside an evolutionary
frame, trying to discern to what extent it contributes to fitness or becomes an
adaptive entity in its own. A similar heuristic can be tried regarding the
opposite tendency: unbelief and atheism, since these cultural phenomena could
help to better adapt to some social settings or become an adaptive sociocultural
niche on its own. The present paper examines some scenarios in which
that question makes sense: the tradition of sociology of religion, with its
different strands, including recent studies on ‘non-religious’; the cognitive; and
the philosophical-theological reflection. The proposed venues show to what
extent the evolutionary model might reveal neglected aspects in the study of
unbelief, and at the same time its limits or the open questions that such
application raise.