The little planet we occupy has orbited a minor star on the fringes of a rather average galaxy in a universe of unimaginable vastness for over 4.5 billion years, yet our particular species of primate arrived on the scene very recently indeed.  It is humbling to realize that, when we liken the age of the earth to the life-span of an average person, mankind has existed for less than the time it takes to say 'Homo sapiens'.