According to the well-known "Doomsday Argument", Mankind has a 95% chance of having reached our half-way point, which in layman's terms means we will be around for another 10,000 years. Hm-m-m.
According to some scientists, however, who have calculated the number of people the planet can reasonably support (food, water and other resources), they seem to think the maximum population could be around 10 billion. And based on current levels and projections, the Earth will hit 7 billion on or around Oct. 31, and, if its projections are correct, we'll reach a population of 9 billion by 2050, and 10 billion by 2100.
The reason for the slow-down can be attributed to a decreasing reproduction rate among humans.
Those scientists figure when the population hits that mark, it will result in a mass, world-wide famine that would wipe us out, as there will be too many mouths open and not enough groceries to shove down all those necks.
I doubt that, for several reasons. First, if a famine did hit, and it wipes out large portions of the population, it would reach the point where there will be more resources left for those who remain. It would be a set-back, like the black plague, but doubtful it would be an extinction event. But I doubt even that will be what happens (though it could well be a part of it).
As we approach saturation of humankind, and long before we hit 10 billion, the growing scarcity of resources - water, fuel, food etc. - will cause nations to go to war. Wars that would kill millions, perhaps billions. And this, too, would reduce the burden on resources.
But setting all of that aside, there is still another scenario. According to the original Hebrew Scriptures of the Bible, when we reach the point where there are as many people living as the number of all those that have passed, that will be the end. Why? Maybe because the Earth and all of its creatures have a finite amount of materials, and once humankind takes up those materials, there is nothing left to sustain us. Or maybe there is just so much "life force" available - that it, too, is limited.
For example, let's say your family of 4 has 1000 kernels of corn. There is no more, anywhere. That's it! Normally, you could each only eat 200 (800 in all) and save the remaining 200 for growing more. Sustainability. But now lets say you have one more child, and that child also eats 200. Now all the corn is being consumed, with nothing left over to grow another crop. Starvation instead of sustainability.
Once mankind, itself, makes up most of the Earth's resources, extinction follows. The fact remains that the laws of physics state that matter can be converted, but it cannot be created nor destroyed. There is a finite amount of matter on Earth. When it is all being used simultaneously, we're in BIG trouble. Once you have used up every grape, there can be no more wine.
Estimates show that the living population and the past population should equal out sometime in the next 50-400 years, give or take a day or so.
And that is precisely why Man has been looking to - and trying to get to - the stars ever since the Tower of Babel. It is our only hope of staving off extinction. Colonizing, mining and otherwise obtaining more matter - food, water, fuel etc. And ROOM. We take up a lot of space - not just our bodies, but also our homes, schools, roads, businesses, utilities - and even cemeteries. If you think rush-hour traffic is a b*itch now, wait until the population doubles, but the amount of land does not!
So, what do I think we have time for?
I think we have time for another martini. Seriously, though, I would not want to make a prediction because there are too many unknown variables. Will we get hit with a new plague? What about a nuclear war? Or slammed by a space rock the size of Manhattan? Will our rate of infertility keep increasing? Or the rate of non-child-producing gays grows exponentially? Ice age? Global warming?
I'll be satisfied if I just make it through another April 15th tax deadline...