## Monday, February 27, 2023

### On Population Chaos

On Population Chaos

This essay discusses four models of population dynamics. The models are: exponential growth, population spike, demographic transition, and population chaos. They are, respectively, naïve, pessimistic, optimistic, and realistic. This essay then delivers good news and bad news about the far future.

In exponential growth, in each generation the population grows by an amount proportional to the population:

P(n+1)  =  P(n)  +  r * P(n)

P(n) is the population in generation N, and r is the growth factor.

If r<0 then this is an exponential decay, which soon reaches zero. If r>0 then this is an exponential explosion, which soon reaches unrealistic levels. For instance, at a 1% growth factor, the population expands by a factor of more than a googol in less than 24000 generations. Absurd! This model is naïve.

In a population spike, the population explodes exponentially until a certain point, then it decays exponentially:

P(n)  =  P0 * (1+r)n  ,  for n<0  and with r>0;

P(0)  =  P0 ;

P(n)  =  P0 * (1+R)n  ,  for n>0  and with R<0 .

This is a pessimistic vision of over-reach and extinction.

In the demographic transition, population growth is limited. The recursion equation is:

P(n+1)   =   P(n)  +  K * P(n) * ( L – P(n) )

If K is negative then the population goes extinct. For moderate positive K, then the population grows up to the limit L, stops there, and remains there. This model is conservative and optimistic.

Population chaos occurs when the factor K is too big for stability. The population doesn’t stabilize at its niche-size; instead it overshoots on the way up and on the way down. The system has sensitive dependence on initial conditions; small causes can have big effects; so its vacillations are unpredictable. The species must adapt to the dangers and opportunities of both overpopulation and underpopulation.

I was taught the exponential model, but I rejected it as unrealistic. I feared the population-spike, and I hoped for the demographic transition; but the population spike is for a worse world than ours, and the demographic transition is for a better world than ours. The most realistic prediction for our world is Nature’s way: population chaos.

The 20th century was an expansion phase of population chaos. The explosion will peak soon, due to the global baby bust, caused by urbanization, economic pressure, and ecological limits. I predict that the mid-21st through late 22nd century will witness population implosion. Then there will be rebound, overshoot, re-collapse, and so on. The chaos will last for centuries, and maybe millennia.

Population chaos implies cultural chaos. Sexual customs will vacillate in phase with economic and ecological pressures. The resulting reversals in law and custom will be attributed to human rights or divine intervention; in reality they will depend on if raising children is worth the price. To breed or not to breed? That is the question.

Those who wish to control the chaos by policy must note that outdated policy is part of the chaos. What was conservative is now radical, and vice versa. I could name names, but that would just add to the chaos. The best response to chaos is to adapt.

Population explosions increase variation. Population collapses increase natural selection. Variation and selection, in quick succession, hasten evolution. Therefore the coming millennia of population chaos will be an evolutionary punctuation event. We will evolve, rapidly.

So will the natural world, for it will collapse when we explode, and explode when we collapse. So if you think that raccoons have clever hands, now, and that kudzu is invasive, now, then just you wait!

I predict that far future humankind will be superior to us in intelligence, empathy, resilience, endurance, courage, wisdom and cunning. They will be athletes, acrobats, singers, artists, poets, and lightning calculators, from an early age. Their immune systems will easily defeat all parasites, bacteria, viruses, prions, and toxins. They will have superhuman compassion, superhuman bullshit detection, and a superhuman sense of humor. And they will have many other gifts. That’s the good news.

The bad news is that they will need all of those superhuman gifts to survive long enough to reproduce.