"If you know a thing only qualitatively, you know it no more than vaguely. If you know it quantitatively - grasping some numerical measure that distinguishes it from an infinite number of other possibilities - you are beginning to know it deeply. You comprehend some of its beauty and you gain access to its power and the understanding it provides. Being afraid of quantification is tantamount to disenfranchising yourself, giving up on one of the most potent prospects for understanding and changing the world" 

                                                                               Carl Sagan - 'Billions and Billions' 1997. paperback version, Chapter 2 (The Persian Chessboard), page 23. 

 

References to size of population over the years

Time and All That.

Europeans and Maories