People have lived on Earth for two million years. For
most of that time, the population has remained
small, as the number of births has more or less
equalled the number of deaths. Improved medicine
and health care, better sanitation, improved farming
methods, producing more and better food, and less
physical work have all led to fewer infant deaths
and more people living longer. ---- Today the world’s
population is nearly 7 billion, and is rising at the
rate of about one million a week.