Reality Blind - Vol. 1

with beneficial mutations that can survive and even thrive in the new environment. For example, let’s say a burrowing species had some individuals who could hibernate longer than the others. During normal times this would be neither good nor bad. But if an event happened where coming above ground at the normal time meant death, then the species would now survive because of what had before been “unnecessary” mutation. If an organism had to wait for a lucky cosmic ray strike to alter just the right DNA base- pair in just the right sperm cell in the “nick of time” to adapt to some new situation, it’d be out of luck. Adaptive plasticity is very important. As you may have surmised by now, a genetic bottleneck is the result of a population being reduced to a very few individuals. Even after their numbers rebound, the population only contains the genome which had been contained in the survivors, with the priceless treasure of accumulated hidden genetic variability mostly lost to the bottleneck. Such populations are thus more fragile against many kinds of challenges, even if they manage to surpass their prior population numbers, until they once again slowly accumulate the capacity for rapid variability in the face of change over many generations. Several of the species taken off the endangered species list because of an increase in the number of individual animals (e.g. the cheetah) are now so genetically similar that they are vulnerable to environmental stressors: the lingering price of having traversed a population bottleneck. The tools of molecular biology can “read” the DNA of an organism and a population and see past near-extinction events, such as the Toba event for humans, (and confirm falsified bottleneck events like scriptural floods). The history of all life is written in its genes, and that history has been replete with bottlenecks. Pretty much all extant life “just squeaked by” so mewhere in its deep evolutionary past. We now find ourselves on the doorstep of Earth’s sixth global mass extinction event of the last half -billion years: a world of proliferating bottlenecks . Because the concept of a bottleneck is so useful, your authors have extended it to coin the term generic bottlenecks to describe aspects of the present human and Earth-system condition and its myriad subsets. Just as in population bottlenecks, the factors which allow the ongoing survival of a process can narrow; for i nstance “supersonic airliners” failed to thrive due to rising fuel prices, competition with longer-range subsonic craft, and decreasing tolerance of “sonic boom” noise pollution - they declined to a just a few routes and ultimately disappeared. These “walls of the bottle”


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