Do the living outnumber the dead?
This question first became popular in the 1970s, a time of population explosion when overpopulation was a widespread fear. The short answer is no. But it is possible - there may come a point in human history where the number of people alive is more than the number of people who have ever lived. This seems unlikely, unless the death rate drops near zero and people have lots of babies really fast (or artificially birth them). But it nevertheless poses an interesting angle of analysis for the population of a species.
I don’t quite know how to project into the future of human growth, but I can at least ask what percentage of all humans are alive today. The best source on this is by the PRB (which stands for the Population Refence Bureau).
Some interesting notes: human life expectancy was around 10 years for most of human history. That required a birth rate of 80 live births/1000 just to sustain the population. For context, a high birth rate today is 35-45/1000, only seen in some sub-Saharan countries. I do wish there was some estimate for “adult” lives lived before 1AD, because 55B does strike me as rather high. If a 10 year life expectancy was the average, what was the distribution?
It is also striking that the human population barely increased for the 1,200 years commonly referred to as the “Dark Age” - but has increased 6x in the last 150 years. Then again, the Black Death is estimated to have killed 100M people. I don’t know how we would actually react to something of that magnitude wiping 20% of the world (and no, Covid came nowhere near, even in the worst possible projections).
But we’ve found our answer: according to these estimates, the number of people alive today represent 6.7% of all humans ever born. Based on current trajectories, it seems unlikely that we will ever reach the point where the living outnumber the dead. But maybe unbelievable medical advances increase our living:dead ratio from 1:15 to 1:1 - then what? I’m not really sure, but it feels like it should be a momentous event for a species. But then again, maybe the human population plateaus (by some estimates at 9B), and we become the first generation to live during a time where the human population is no longer increasing.
I’m not sure why I find the thread of human population so interesting, but maybe it’s just because it gives me a broader context to measure our human achievements.
If you’re interesting in going further, there is pretty interesting math behind population growth using a logistic map, period doubling bifurcations, and, yes, even fractals.