Population

The figure is debatable, but it seems reasonable to assume that something like 100 billion people have ever lived on Earth, if by "people" we mean Homo sapiens sapiens, our little twig on the evolutionary tree after its most recent separation from some other line of hominid creatures that we define as nonhuman. This happened something like 5 million years ago, though again, the actual figure is in debate. Nevertheless it must be something over 2 million years and less than 8 million years, since we have strong fossil evidence in both directions from those dates.

Think about that for a second. There have been 100 billion human beings ever in the history of time, and 6 billion of them are alive right now. If we only count people who've lived in historical times (since the invention of writing), that 6% figure might jump to something like 35%. It's astonishing to realize that a huge chunk of human history is happening in this span of years that is so puny on a geological and even biological scale.

The human population has exploded. We were condensed into a relatively small are - the arboreal highlands of eastern Africa most likely - for most of our past. Something (climate change, perhaps) caused us to come down from the trees and adapt to life on the savannah, and from there things started to snowball and people spread all over the earth. The actual population size was still small, though; perhaps a few tens of thousands, certainly less than a million.

Then we learned to farm and herd. It's debated when this happened and why, and which came first (certainly herding in my estimation), but these technologies enabled humans to stop wandering after game and put down roots. Cities were born, and with them, division of labor. Soon there were kings, priests, soldiers, farmers, craftsmen, civil servants, artists, and so on. The fact that society could now support some portion of itself not tied to manual labor in pursuit of food or shelter meant that lots of esoteric things could be thought about and produced.

That led to smelting, tanning, writing, astronomy, and the rest of it, and soon enough Rome became the first city in history to have 1 million residents. Things hit a bit of a bump in the road with Rome's fall (though not nearly so much as you might have been taught in school), but soon enough London emerged with 2, and then 3 million inhabitants, and more importantly, was the site of the industrial revolution, where people began to mechanize labor. This produced an enormous surplus of available resources, and, predictably, human population exploded.

And what an explosion. When I was born in the 70s, there were 3.5 billion people. We've practically doubled now to 6 billion. The 60s and 70s brought fears of a Malthusian-type explosion leading to mass starvation, but the population growth rate seems to be declining so that the next 30 years likely won't see another doubling but rather a more modest increase. That is, unless fossil fuels are replaced with some even more readily available energy source. Cheap fusion, for example, could cause another population explosion. Such an explosion would necessarily mean a push into space, to the moon or mars or beyond, since the Earth's viability as a habitat would be jeopardized by so many people.

There is lots more to think about and talk about when it comes to population growth and control. I've only just brushed the surface here, and it is a fascinating field, if you're of a mind to be fascinated by such things (exponential growth, limiting factors, and so on). I believe a basic knowledge of ecology in all its subdisciplines must be learned by everyone who shares this planet, or we risk bringing about our own destruction through ignorance.

And it still blows me away that something between 5% and 10% of all people who have ever lived, are living right now.