I started teaching in 1976 and population was a major issue. Population Concern published great posters. Since then the world population has gone up from 4.2 billion to 7.6 billion. All those extra mouths to feed, bodies to house and clothes, excrement to be disposed of. Population growth has ceased to be an issue in much of Europe with a birth rate below 2.1, but immigration has become a major issue. In the same time period the population of Africa has almost trebled, SE Asia doubled.