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7 Billion People?
On or around Oct. 31, 2011, the world's 7 billionth person will be born, the United Nation estimates.
Even more staggering is that of the 7 billion people on Earth, about 1.4 billion of them will be old enough to have observed the arrivals of the 6 billionth, 5 billionth, 4 billionth and 3 billionth people in the world. About 42.5 million people could have blown the party horn for the birth of the 2 billionth baby.
Yes, population has risen very quickly over the last century. Demographers do expect a decline in the population growth rate, but absolute numbers will continue to rise, likely hitting 9 billion by 2050. Meanwhile, we look back at history's past population milestones, asking: "How has the world changed?"
1805 – The 1 billionth babySlide 2 of 15
1805 – The 1 billionth baby
The world's first billion-person milestone was a long time coming. Estimates of historical populations can be rough, but the U.S. Census Bureau pegs the global population at a paltry 5 million people in 8000 B.C. Certainly, humans remained scarce until the development of agriculture some 10,000 years ago. Even after our kind began farming, it was a slow climb to the 100-million-person mark around 500 B.C.
From there, population growth gets a bit more exciting. Somewhere around A.D. 500 to 600, humans hit the 200-million mark. By about 1250, the population had doubled to between 400 million and 416 million. Plagues and wars took a toll on the global human population before the 1400s, but the numbers then started a steady tick upward. [Infographic: Urban Population Explosion]
The birth year of the world's billionth baby will never be certain, but it's likely he or she came into the world around 1805. Beethoven was big that year, and already going deaf. Lewis and Clark made it to the Pacific Ocean. Napoleon was on a roll in Europe, 10 years from his defeat in the Battle of Waterloo. With the exception of a few coastal outposts, most of Africa was a complete mystery to Europeans. In China, the Qing Dynasty had just put down the White Lotus Rebellion, a tax protest that ultimately killed about 16 million people — a reminder that mass death and population growth don't necessarily cancel one another out.Slide 3 of 15
1927 – Race to 2 BillionSlide 4 of 15
1927 – Race to 2 Billion
It had taken thousands of years for the population to reach 1 billion, but 2 billion was barely more than a century away. The 2 billionth baby was likely born in the late 1920s, perhaps 1927; the U.N. estimates that by 1930 there were 2.07 billion people on the planet.
This sudden takeoff of population makes sense in the context of a phenomenon called the demographic transition. In the transition, a population goes from one with high birth rates and high death rates (imagine farming families having seven or eight kids in hopes of a few reaching adulthood) to one with low birth rates and low death rates (where parents usually have one or two kids and expect them to grow up).
In the midst of this transition is a period when death rates are declining but people have yet to alter their behavior: They still have lots of kids. Even if those kids decide to have only a few children of their own, population will remain high, because there are so many potential parents.
The agricultural and industrial revolutions led to gradually declining death rates in the Western world starting in the 1700s, while birth rates remained fairly high for generations. As developed countries began to see falling birth rates, developing countries entered the transition period of declining death rates and high birth rates. Some countries in sub-Saharan Africa are just entering the demographic transition today.
But back to 1927. If the 2 billionth baby was indeed born in this year, he or she came into being the same year that the first trans-Atlantic telephone call was made (from New York City to London). The world was on the cusp of the Great Depression. Mao Zedong battled the Kuomintang in Hunan, China, and lost — for a time. An enormous flood along the Mississippi River inundated 27,000 square miles (70,000 square kilometers), the greatest natural disaster in U.S. history at that point (photo shown above in Illinois on March 25, 1927).Slide 5 of 15
1959 - 3 Billion PeopleSlide 6 of 15
1959 - 3 Billion People
The 3 billionth baby was a Cold War baby, born in approximately 1959. If he or she was a westerner, baby No. 3 billion would have been a baby boomer, part of the generation born after World War II. During this period, births in the U.S. rose from around 2.8 million a year in the 1930s and early 1940s to a peak of about 4.3 million births per year in the late 1950s.
Worldwide, the population growth rate hit a peak of more than 2 percent per year in the early 1960s, just after our 3 billionth baby's birth. The growth rate had been increasing since 1950, according to the U.S. Census Bureau, with one rapid downward plunge between 1959 and 1960. This hiccup was because of China's Great Leap Forward, a disastrous industrialization and collectivization push that killed millions and caused China's fertility rates to plummet. (Shown above: a Communist monument on Tiananmen Square in Beijing, China.)
The year the 3 billionth person was born was also the first year that rocket scientists were able to send monkeys to space and bring them back alive. The Dalai Lama fled Tibet during an uprising and set up a government-in-exile in India. And in a fitting tie to humanity's evolutionary roots, Louis and Mary Leakey discovered the first skull of the ancient hominid Australopithecus.Slide 7 of 15
1974 - A Billion MoreSlide 8 of 15