The Fate of Humanity Part 3: How many of us will there be?

Jared Diamond wrote this famous essay in 1987, although the link is to a 1999 reprint. He calls the transition from hunting and gathering to agriculture "The worst mistake in the history of the human race." He seems to have a point. Hunter-gatherers were healthier, taller, lived longer and had more leisure time than farmers. In fact life expectancy at birth pretty much throughout the planet fluctuated in a narrow range of around 40-45 years from the dawn of agricultural civilization some 12,000 years ago (and more recently elsewhere of course) until the late 19th Century. And in all that time, the majority of people lived at a bare level of subsistence, although the agricultural revolution did enable priestly and warrior castes to capture surplus and rule over the masses. Hunter-gatherer societies, in addition to being relatively healthy, are egalitarian. The reason people adopted agriculture was not because it made them more prosperous, but because it was necessary to support the growing hunter-gatherer population.

But then population growth pretty much stalled. Until something happened.



There began to be a bit of an increase at the end of the Middle Ages, but the really dramatic inflection point is in the late 1700s. Life expectancy began to increase linearly in many places in the early 1800s. According to an analysis published in 2012, Swedes for example had life expectancy similar to that of hunter-gatherers in 1900, and now of course their life expectancy has nearly doubled. For the total size of the human population, what really matters is the number of women who live through childbearing age. Many people used to die in infancy and childhood and many women died in childbirth. In the wealthy countries, those events are now rare. The population explosion is not because most people now live into their seventies, but because so many make it through their 30s.

In any event, the impact of the 20-fold increase in the human population since 1750 is what we have seen in the past 2 posts -- the conversion of half the world's arable wilderness to farmland, depletion of water resources -- and a whole lot more, including the massive carbon emissions that are changing the climate, mass extinction, and millions of refugees. In case you believe claims by some that the world has become more peaceful, nope.

Wars between states are less common and deadly, but civil conflict has been raging since the end of WWII. Resource shortages have a lot to do with this. We are now witnessing the highest levels of displacement on record. An unprecedented 68.5 million people around the world have been forced from home. Among them are nearly 25.4 million refugees, over half of whom are under the age of 18 There are also an estimated 10 million stateless people who have been denied a nationality and access to basic rights such as education, healthcare, employment and freedom of movement.

Can the planet support 10 billion people? And what happens after that? Well, it might help a bit if we had a more egalitarian world society. The situation has actually grown worse since this graphic was made. We can bring up the standard of living of the poor and actually decrease total consumption if we do something about the super-rich.



But there's something else we can do.  Raise the status of women.

When women are educated, they have fewer babies. A key U.N. Millennium Development Goal was universal access to reproductive health and family planning services. Allowing families to plan the number and timing of their children reduces infant mortality rates and improves the health of both women, and their families. The very conditions that will help the population stabilize are also good for society; they help families’ live longer, healthier lives, raise healthier children, and have more opportunity to contribute to their nations and families’ prosperity. 

So if we're going to be around much longer, we need to have a more egalitarian world. It needs to be a world in which women and men are equal, in which a small class of super-rich people does not parasitize the rest of society, and in which we change our way of life to make our presence of the planet more tolerable.