Evolutionary predisposition is the analysis du jour when
describing all of human behaviour. These days everything we do--
from appreciate music to donate to charity--evidently boils down
to our desire to lure a mate and make many babies.  Now it seems
a scientific study has proven an evolutionary reason for
depression:   A study published this month in the Journal of
Personality and Social Psychology suggests this clever idea
might even be true.  Carsten Wrosch from Concordia University in
Montreal and Gregory Miller of the University of British
Columbia studied depression in [97] teenage girls... Their
conclusion was that those who experienced mild depressive
symptoms could, indeed, disengage more easily from unreachable
goals. That supports Dr Nesse’s hypothesis. But the new study
also found a remarkable corollary: those women who could
disengage from the unattainable proved less likely to suffer
more serious depression in the long run.  The conclusion to this
study is that mild depression is in fact a healt