Not vague at all I think. Everyone knows in what context the question was asked...it's not an original one. For me, there is no reason other than the numbers were in our favour. Pure chance
I voted for the last option - lets see, we SHOULDNT just destroy, we HOPEFULLY make great works, we SOMETIMES spread our genes (but not everyon does), yet we ALL wonder about life and our purpose now + again. There should be a 5th option, "To enjoy our lives and each other.."