An evolutionary bottleneck is a metaphor used by evolutionary biologists to refer to an apparent acceleration of genetic variation in a species due to a catastrophic reduction in its population. Unlike the normal processes of natural selection, which are driven by "fitness" or the adaptive benefits of a given allele (variant within a specific genotype) within a given ecological niche, evolutionary bottlenecks tend to result in the rapid proliferation, in a recovering population, of random alleles that may or may not confer reproductive advantage. If they do not, the population may quickly go extinct, due to a loss of adaptive fitness; conversely, if they are lucky, a random allele may confer a benefit that gives them an edge over competition or over their prey, and enables them to rapidly proliferate, taking over one niche and expanding to others.
A currently popular theory in human evolutionary biology is that one or more evolutionary bottlenecks--disasters that nearly eliminated our hominid ancestors but left a small remnant to survive and proliferate--may have, through this evolutionary process, conferred upon us the selective advantage that resulted in our taking over the entire planet: our unique aquisition of digital language, which enabled us to communicate not just nonverbal relationship information (e.g. dominance/submission, sexual interest, or parental guidance) but actual concepts and propositions, invented and shared as needed--a communicative intervention that gave us a decisive evolutionary advantage over all other complex species--plant and animal alike, and that led, through a familiar process of positive feedback, to the expansion of our frontal lobes that enabled us to process this vast and growing array of information.
The results today, of course, are entirely predictable from an evolutionary perspective. As biologist Lynn Margulis once observed, "Humans are an extraordinarily successful species, but extraordinarily successful species never last long." This is true because such species, no matter how versatile, quickly outgrow the carrying capacity of their ecological niche--even if that niche comprises the entire planet.
And that is exactly where we are today. There are far more humans alive today than all of our ancestors combined, and most of us--especially in the global North--are using far more energetic, biological, and material resources per capita than our ancestors ever imagined. As a consequence, ecosystems are collapsing everywhere, topsoil is being depleted at a far faster rate than it can be rebuilt, our fisheries are declining rapidly, and of course the climate crisis is the wild card that could upend it all within the coming decades. The possible triggering mechanisms of global catastrophe are proliferating, almost daily: rapidly melting ice caps and glaciers at both poles and on mountains worldwide; an accelerating uptick in the frequency and severity of droughts, floods, violent storms, and wildfires; the potential collapse of the international political and economic order into warring authoritarian states ruled by thuggish despots (which could easily lead to the unimaginable outbreak and proliferation of nuclear conflicts)--the convergent prospects of global biological and civilizational collapse are all too clear, leading the most pessimistic of us to warn darkly of "human extinction" within the next few decades.
Extinction? Possibly, but I doubt it. But a great die-off of a huge proportion of humanity is probably inevitable--and it won't be pretty. Imagine, for example, if Thwaite's Glacier in West Antarctica, which holds back the huge mass of ice on the West Antarctic Ice Sheet, were to collapse within the next few years, as many scientists predict. This could trigger a cascading collapse of the entire western continental ice sheet, raising the global sea level by three meters. (This is why it is often called the "Doomsday Glacier") The result would be the inundation of coastal cities throughout the world, resulting in a surge of destitute refugees inland, spawning predatory gangs that survive by raiding shopping centers, then suburbs, then farms--and governments, despite their armed forces and brutality, would be powerless to stop them. Whole economies would quickly collapse, leading to mass starvation, yet more desperate refugees, more violence, more starvation...the mind reels at the horrific prospects worldwide. And coupled with increasing drought, violent storms, and wildfires, the global death toll of humans and other animals would continue to spiral out of control.
But would we all die? I doubt it. The most likely survivors would be the most resilient: small bands of people with practical skills who form close working relationships--either for more effective predation (like our current urban drug cartels and criminal syndicates) or for more adaptive purposes. But if only thugs survive, they will eventually kill each other off, competing for supremacy. And who wants to live in a desperate, broken world of scattered thugs and warlords anyway? Not I.
So what might be "more adaptive purposes"? If we go back to past Dark Ages following catastrophic collapses (e.g. the Eastern Mediterranean collapse of the 12th Century BC, or northern Europe following the collapse of the Roman Empire, we see long periods of rival warlords and clans, holing themselves up in defensive battlements and fighting endless power struggles--but we also see a "saving remnant" of scattered communities with higher, regenerative goals--like the monasteries which preserved and disseminated literacy and both classical and biblical texts, or even the nomadic Bedouins who carried the Qu'ran to the far reaches of Asia and Africa; like Buddhist communities in war-torn India and central Asia, or Confucians and Taoists in the wake of the chaotic Warring States period in China.
Could something similar-- small, scattered communities of Gaians that preserve the best of the past along with a more adaptive, aware, and compassionate way of living within, and regenerating, our biological support system--happen again after the coming global catastrophe? I don't know--but it is an ideal worth living for, and worth passing on to our younger generations. For now, our best bet is to propagate Gaianity by growing gardens, growing community, and growing awareness.
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