Fear of mass destruction

Perhaps I have watched one too many apocalyptic movie, but I find myself musing on our collective fear of mass destruction.

Have you noticed that we, as a species, seem to be obsessed with death? It is not just the fear of dying that we all face, but a generalised fear of destruction.

Where did this fear that we will be destroyed on mass, whether by our own hands or some external event or unknown threat, come from? What underlies it? And, perhaps more importantly, how does it adversely (or positively) impact our collective endeavours?