## March 27, 2008

### Percentage Of Humans Ever To Live Who Are Alive For New Millennium

Stupid Question ™
Dec. 30, 1999
By John Ruch

Q: What percentage of humans who have ever been alive will be alive for the new millennium?
—J.M.

A: Even the best authority on this topic refers to the calculation as “alchemy”—though that hasn’t prevented social scientists from taking a crack at the question (basically, “How many people have ever lived?”) since at least the late ’50s.

How do you define any of the key terms: “human,” “alive” and even “millennium”? (We’ll just say Jan. 1, 2000 for the latter one—this is our Y2K issue.)

Various calculations over the years have universally considered “alive” to mean “been born.” That’s because birth rate is essential to the calculation.

“Human” is trickier. Modern Homo sapiens go back anywhere from 30,000 to 200,000 years, and the very similar Homo erectus to about 1.5 million years. Calculations are generally made from an original population of 2, but even that might not apply to Homo sapiens, which may have arisen independently in several areas.

Presuming we can choose a “start date” for humanity, the math calculations that follow are extremely sketchy. They take some key historical population estimates, estimate life expectancy and birth and death rates at those times, then extrapolate forward and backward in time. The result is a highly speculative, probably artificially smooth growth curve from a very low early population to a high modern one.

Even current population figures are educated guesses that vary among sources (though hovering around 6 billion).

All that being said, the definitive calculation was made in 1995 by Carl Haub of the Washington think tank Population Reference Bureau, who updated his figures for me.

He starts conservatively, at 50,000 BC, with a population of 2. Like everyone else, he figures the birth rate was very high, and so was the death rate. World population in AD 1 is estimated at 300 million; in 1650 at 500 million.

By 1800, the Industrial Revolution had lowered death rates and population was at 1 billion. Post-World War II, death rates plunged further and population skyrocketed.

In short, Haub estimates 151,122,380,169 births since 50,000 BC, with the great majority dying as infants. He also estimates the population on Jan. 1, 2000 at 6.017 billion. Therefore, on that date, about 6.6 percent of humans ever to live will be alive.

Haub’s estimates are conservative; competitors have calculated generally higher numbers, some as high as 10 percent. Since this is all half-hooey anyway, it’s safe to say about 8 percent.

It’s a small percentage, but a big number. Consider this: There were more people alive in 1980 than were born in the entire pre-agricultural age (before c. 8,000 BC), even with its high birth rates.

And in terms of actual population, there are more people alive on Earth right now than at any other time.