Happy birthday. The topic for my Monday illustration was quite easy to pick. The world population passed the 7 billion limit and several different babies were celebrated as the one to break the limit. Demography and especially historical demography is interesting. Read Massimo Livi-Baccis book A Concise History of World Population if you want to know how wars and diseases, beliefs and ideologies, changes in climate and innovations in food production affected the population through time. It was on the reading list for one of my courses a few years ago when I still pretended to be a history student, and really stood out as good reading. The latest edition is from 2006 and updated with projections to 2050.