7 Gpeople

While at a conference in Istanbul, I went to the İSTANBUL ARKEOLOJİ MÜZELERİ, which was an absolutely fascinating archeology museum. Istanbul has featured prominently in the growth of civilization, and I struggled to keep track of the many different civilizations and cultures that occupied the region at one time or another. I had to find a youtube video to help me sort it out.

There was a very nice exhibit on Troia (Troy), which apparently really existed; it's ruins were unearthed in a farm field not too far from here. It was settled, destroyed, and resettled in 9 different epochs before being ultimately abandoned. Even back then, it seems that anything you dug up had a 1000-year history. Buildings were built on top of buildings. The reconstruction of the different settlements was interesting.

It was really hard for me to get my head around how small cities were in comparison to now. Istanbul currently has 13 Mpeople living in its greater metropolitan area. In 3000 BC, that was the human population of the world. The largest cities in antiquity were ~250 kpeople. It made me wonder if all of our advancements in technology and culture in the last couple hundred years could be attributed strictly to 1) more people to do the work and 2) longer tails on the normal distribution of people with various abilities.

So just how many people were there as a function of time? The log-log plot above from wikipedia shows current best estimates. Apparently, some 70 kyears ago, possibly as a result of a major volcano eruption, the human population was reduced to something on the order of 1000 to 10,000 "breeding pairs." Since then, the population rapidly recovered to several million, where it remained stable until agriculture was developed. This is all in a nice video tracing genetic migration via mDNA.


Since then, there has been exponential growth (a line on log-log plots) with a transition to a slower growth coefficient at ~400 BC. Occasional Black Plagues aside, the human population has increased dramatically. I remember hearing once that half the people who ever lived are alive right now. That's actually definitely false--it's closer to 6%. Also, everyone seems to think that population growth is accelerating (remember this video from the 80's ?). The graph above definitely shows that's not true, either.

But what is true is that this growth cannot continue unchecked without hitting its head on something, be it food supply, global warming, danger of pandemics, warfare, declining birth rates, or whathaveyou. It's estimated that in October of this year, 2011, there will be 7 Gpeople on the planet. This map shows where the population currently is, but it's estimated that much of the growth in the next century will happen in poverty-stricken Africa. Things pretty much have to plateau around 10 Gpeople, though.

So what to do? The most effective ways to reduce birth rates, which is key to controlling population growth, global warming, saving the environment, and many of the rest of our problems are:

1. contraception
2. improving the standard of living (ending poverty)
   
3. education (and education about contraception)
   
4. and reducing infant/child mortality

That last item is counter-intuitive. The reason it is important is that when survival rates are low, couples have more children to compensate, including a buffer for uncertainty. Having a predictable path from birth to adulthood allows for more precision in family planning.