SAN ANTONIO, Tex (Reuters) -- The seven-billionth human is expected to be born on Monday, but an expert who helps do the counting says that event comes as the Earth undergoes a demographic shift toward slower population growth.
According to the United Nations Population Fund, the seven-billionth child is most likely to be a boy born in India or China, but the trend of fertility in the longer term is in a different direction, says Dudley Poston, a professor of sociology and demographics at Texas A&M University,
For the first time ever, the human reproduction rate is slowing, in many places slowing significantly, and the slowing growth is not only happening in Europe and Japan, he says.
"Once your fertility rates drops below two, it is very very hard to get it to go back up again," Poston told Reuters.
"We now have 75 countries in the world where the fertility rate is below two," meaning the average woman is having fewer than two children.
That is far below the rate of 2.2 to 2.3 considered optimal to hold the population steady, factoring in the number of females who have no children or who don't live to reach childbearing age.
While he says Europe and the industrialized democracies of east Asia are the 'poster children' for demographic shift, low birth rates are also being seen in Brazil, in China, and in the Islamic Middle East, where the fertility rate in the United Arab Emirates is 1.8.
"Japan is losing more people today than they're gaining," Poston said. "South Korea has an alarmingly low fertility rate, 1.1."
Not long ago, the opposite was true. In 1970, the average fertility rate worldwide was 4.5, leading to predictions of demographic doom in books like Robert Silverberg's "The World Inside" and Stanford University biologist Paul Ehrlich's "The Population Bomb."
They saw a world where hoards of wildly reproducing humans desperate for dwindling food supplies would destroy social cohesion and spark wars and societal unrest.
But a funny thing happened on the way to population Armageddon. Poston says the fastest growth period in the history of the world was in the mid to late 1960s, which prompted dystopic predictions.
"When Paul Ehrlich wrote that book the world was growing at about 2 percent per year," Poston said. "Now we're growing at about half that."
Poston says a combination of factors led to what may be the most significant demographic shift ever. In the industrialized West, improved methods of birth control and greater opportunities for women in the workplace and in society meant the end of 5,000 years of women generally being considered society's baby-makers.
In China, there has been aggressive enforcement of a 'one child' policy, drastically reducing population growth rates, and leading to a surplus of males.
Worldwide, urbanization has reduced the need for large families beneficial in rural agricultural areas.
Reasons for significant growth rate declines in places like Iran, where the rate has fallen from 7.0 in 1974 to 1.9, remain more of a mystery, but Poston says they probably can be traced to cultural changes that can be very difficult to reverse.
"We have been growing very, very fast in the world and now we're starting to slow down."
Poston says it took until about 1800 for the earth to see its one billionth resident, as high fertility rates were effectively countered by high infant mortality rates, diseases, and nearly continuous warfare that generally cut down men at the height of their most active reproductive years.
The march of science led to a decrease in infant mortality and deadly diseases, and combined with a continued high fertility rate led to a huge population bloom. The two billionth human was born in 1930, and the six billionth in 1999.
Moreover, the warfare and constant societal violence that helped keep the population in check has retreated, Harvard University psychologist Steven Pinker says in his recent book "The Better Angels of our Nature."
"It is really only in the countries of sub Saharan Africa where fertility is still high...," Poston said, "but even in several of these countries there have been fertility declines in recent years."
So Poston says while it took 12 years to reach Monday's seven billion mark from six billion, it will take 14 years to reach eight billion -- the first time in history a billion milestone has taken longer to reach than the one before -- and then 18 years to reach nine billion.
Thus far the world has been able to produce enough food to feed its new mouths. The U.N. says world food production per person today is 41 percent higher than in 1961, thanks largely to the "Green Revolution" in farming which brought higher yields not only to Western farmers, but brought traditional subsistence farming in Africa and Asia into the modern age.
Food production per capita in India today is 37 percent higher than fifty years ago, according to the World Bank.
Some still fear food shortages and price rises, and problems with supplies of other commodities like oil.
"(Whether) the rate of farm production slow down or level off is uncertain," Poston said. "But right now there is no difficulty."
And the trends may bring problems of a different sort, he said, predicting the world will begin seeing the impact of declining populations in as little as 40 years.
"That is going to be the issue in the future," Poston said. "We are going to have to start thinking for the first time in human history about fewer."
That will mean thinking in an entirely new way about everything from resource production to old age pensions, he said.
Editing by Jerry Norton