3. Diversity is the only way
From 'Permian-Triassic Boundary Outcrop'. Photo by
252 million years ago a chain of events produced the so called Permian–Triassic (P–Tr) extinction event — a catastrophe that affected so deeply the terrestrial ecosystem that it is conjectured “it took some 10 million years for Earth to recover” from it. Nevertheless, the Earth ultimately did recover from it, which led to so big a change in natural history that scientists had to clearly separate what was before from what followed — the Paleozoic (“Old Life”) from the Mesozoic (the “Middle Life”). Among the many important questions that raise when considering so catastrophic an event, some that I feel are particularly intriguing are:
- Q1: Was there any “common reasons” behind the P–Tr extinction event? In other words—were there “common triggers” causing such a widespread correlated failure?
- Q2: What was the key ingredient — the key defensive strategies that is — that made it possible for the Earth to survive in spite of so harsh a blow?
In order to attempt to formulate an answer to the above questions, now I recall the following facts:
- F1: “Mineralised skeletons confer protection against predators” (Wood 2018, Knoll 2003)
- F2: “Skeleton formation requires more than the ability to precipitate minerals; precipitation must be carried out in a controlled fashion in specific biological environments” (Knoll 2003).
- F3: “The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on ambient CO2 levels to produce their skeletons” (Wikipedia 2021).
The three facts tell us, respectively, that:
- One of nature's many independent evolutionary paths was particularly successful (F1) and thus became widespread.
- Regrettably, the adoption of the solution implied a strong dependence on predefined and stable environmental conditions (F2).
- A correlation exists between the class of species that adopted the solution and that of the species that were affected most by the P–Tr extinction event (F3).
A similar scenario can be drawn for very different stages. For instance, in computer systems, we could imagine that
- A certain solution becomes widespread (for instance a memory technology, a software library, a programming language, an operating system, or a search engine).
- The solution introduces a weakness: for instance, a dependence on a hidden assumption, or a “bug” depending on certain subtle and very rare environmental conditions.
- The weakness translates into a common trigger, a single-point-of-multiple-failures. One or a few events could “ignite” the weakness and hit hard on all the systems that made use of the solution.
What can we conclude from the above facts and analogies? That solutions that (appear to) work well in the “common case” are those that widespread more. Regrettably, this decreases disparity, namely inter-species diversity. Species that externally appear considerably different from each other in fact share a common trait — a common design template. This means that whenever the “common case” is replaced by the very rare and very dangerous “Black Swan”, a large portion of the ecosystem is jeopardized. In fact, the rarest the exceptional condition, the more widespread is the template and the larger the share of species that will be affected.
This provides some elements towards an answer to question Q1: yes, there were common triggers that ultimately produced the P–Tr extinction event by increasing the diffusion of the same “recipes” thus paving the way to large amounts of correlated failures. On the other hand, the Earth did survive the Great Dying and other extinction events. Why? My guess, which also constitutes a tentative answer to question Q2, is that Nature introduces systemic thresholds that make sure that disparity never goes beyond some minimum. The key ingredient to guarantee this is diversity: it is not by chance that mutation is an intrinsic method in genetic evolution. Mutation and possibly other mechanisms make sure that, at any point in time, not all of the species share the same design templates. In turn, this guarantees that, at any point in time, not all the species share the same fate.
The major lesson we need to learn from all this is that diversity is an essential ingredient to resilience. Spread the use of a “general solution,” and you will bring down diversity, thus decreasing the chance that the ecosystem will be able to withstand the Black Swan when it will show up.
And if the general solution has not been tested for long-term side effects, the black swan may show up much sooner than expected.
By avoiding a single, global strategy, even when that strategy proves wrong or counter-productive, still the damage will not be global and full. The few that did not comply will be able to pass through the sieves of the Black Swan with limited damage.
- Knoll, A.H. (2003): Biomineralization and evolutionary history. Reviews in Mineralogy and Geochemistry 54, 329-356.
- Wood, R. (2018): 'Exploring the drivers of early biomineralization', Emerging Topics in Life Sciences. https://doi.org/10.1042/ETLS20170164.
- Wikipedia (2021): 'Permian–Triassic extinction event'. https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event
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