The Great Filter hypothesis -- a new Great Filter?
Darren J. Dougan
TL;DR
This paper investigates whether depopulation could be a universal Great Filter that helps resolve the Fermi Paradox, introducing exodemography and exospecies as the relevant framework. It uses standard population-dynamics formalisms, defining $n(t)$, the growth rate $g= rac{1}{n} rac{dn}{dt}$ with $n(t)=n_0 e^{gt}$, and carrying-capacity constraints $ rac{dn}{dt}=g nigl(1- rac{n}{K}igr)$ to analyze human and extraterrestrial trajectories. By contrasting United Nations forecasts with bespoke BQI projections, the paper predicts global $TFR$ approaching $1.5$ by $2100$ and ~ $1.35$ by the $2200$s, potentially driving population toward extinction by the latter half of the millennium (and as early as 2434 under a $TFR=0.6$ scenario), effectively creating a new Great Filter. The work further argues that if depopulation is universal, conscious life may fail to colonize the galaxy, with machines likely remaining non-conscious tools, thereby offering a potential resolution to the Fermi Paradox and prompting new lines of inquiry into exodemography and long-term existential risk.
Abstract
The Great Filter hypothesis is an extension of the Fermi Paradox: "If life is so common in the universe, why don't we see it?" The Great Filter theory posits there are multiple obstacles or filters life must pass through which ultimately sifts out intelligent life. This paper identifies a new filter: depopulation. As an exospecies advances and reaches the top of the food chain on its planet, Darwinian evolution selects the species to breed fewer offspring due to a lack of predation. As the species evolves intelligence, this leads to medicines and most notably contraception, enabling the species to reduce infant mortality while controlling reproduction. Finally, economic, social and educational factors add to the conscious decision of the intelligent life to slow reproduction. These factors are currently contributing to a human global population peak mid century with subsequent population collapse in less than 500 years. Noting that population growth and decline is exponential, our modelling forecasts human extinction thresholds being tested sometime after the year 2500. There is no reason to assume depopulation dynamics (exodepopulation) would not apply to exocivilizations (exodemography), thus providing a possible resolution of the Fermi Paradox. Furthermore, as machines and AI inevitably supplement humans as depopulation accelerates, the Fermi Paradox can be restated as "Why don't we see machines and AI colonising the galaxy?" A plausible answer is machines will not become conscious and will continue to operate only as tools, tools that will cease operating once humanity is extinct. The Fermi Paradox can then be restated as "Machines will not become conscious, otherwise we would see them colonising the galaxy".