From prehistory to today, the people who have trampled our planet have been estimated to have been almost 108 billion. Calculation (simply statistical) is not easy because it depends on many variables.
One of the most reliable studies dates back to the mid-1990s and was conducted by Carl Haub on behalf of the NPO's Population Bureau. The study, titled "How many people ever lived on Earth" was updated in 2002 and 2011.
The author noted that his work could be only semi-scientific, as there were no demographic data for nearly 99% of the time that man lived on Earth.
Estimation was obtained by comparing population levels of 50,000 BC (when modern man appeared) to date, applying, for each historical period, rates of birth assessed on the basis of different criteria: from 8,000 BC to 1 applied a value of 80 born per 1000 inhabitants per year.
In 2011, the minimum value of 23 births per 1,000 people was applied. It was started from a hypothetical number, 2 individuals, to 50000 BC to achieve gradual growth of the population: 5 million in 800 BC, 300 million in the first century AD, half a billion in 1650, and 5 billion in 760 million in 1995.
Millions of millions
Taking into account the progress, according to Haub's 2002 estimates, the Earth has been inhabited - throughout human history - with about 106 billion people to reach 107,602,707,791 in mid-2011. The statistical study conducted by other scientists confirms the estimates Haub, with variations ranging from 100 to 115 billion.
What about the future?
The world population will grow exponentially: in 2050, according to a United Nations report, we can be at 10 billion that populate the planet: Every year, Earth is enriched with 83 million new residents, despite a general downturn of reproduction.