Human population is increasing faster than it has ever done in history. It took about 4,800 years, from 3000 BC, when the world had about 10 million humans, to 1800 when we reaxhed 1 billion. The world's population doubled in the 130 years between 1800 and 1930, when we reached 2 billion. It took 30 years to add the next billion (from 1930 to 1960 we went from 2 billion to 3 billion). The next billion was added in the 14 years from 1960 to 1974, and the next billion was added in the 13 years between 1974 and 1987. The world saw 6 billioin people added in the 12 years between 1987 and 1999. We reached 7 billion 12 years later. We will have 8 billion in 2024, 13 years after crossing the 7 billion mark. (Source: Science, "Population" July 29, 2011, p.540.)
"Future population growth is highly dependent on the path that future fertility takes. In the medium variant, fertility declines from 2.52 children per woman in 2005-2010 to 2.17 children per woman in 2045-2050. If fertility were to remain about half a child above the levels projected in the medium variant, world population would reach 10.6 billion by 2050 and 15.8 billion by 2100. A fertility path half a child below the medium would lead to a population of 8.1 billion by mid-century and 6.2 billion by the end of the century. Consequently, population growth until 2050 is inevitable even if the decline of fertility accelerates." (From: UN Population Division, Department of Economic and Social Affairs, World Population Prospects: The 2010 Revision, the official United Nations population estimates and projections prepared by the United Nations Population Division.)
Ninty to ninty-seven percent of all population growth will be in concentrated in the world's poorest countries. There will be some major shifts in regional demograqphics. The most astionishing is probaly what is happening in Africa. In 1900, Europe had twice the population of Africa. In 2000, the populations were about identical. In 2050, Africa wil have nearly three times the population of Europe. Another shift will see India becoming the world's most populous country, having surpassed China' population by 2020. (Sources: Science, July 29, 2011, p.539 and The Economist, The World in 2050, Wiley, 2012.)
The world will also be older. Those 65 and older will increase in percentage from 8% in 2010 to around 12% in 2030 and over 16% in 2050. In the richest countries many people will have a life expectancy of 100. (The Economist, The World in 2050, Wiley, 2012.)
"Among thr most notable human acheivements ever is the fact that life expectancy, which hovered in the vicinity of 30 years throughout most of human history, rose by more than 20 years since 1950 forthe world as a whole." (Source: Science, "7 Billion and Counting", July 29, 2011, p.562.)
Also see Increasing Humanity.