Evolving towards Extinction

One question that I always had about evolutionary biology was whether it was possible for a species to evolve towards extinction. Logically, it should be possible. Evolution is opportunistic, it always prefers short term solutions and if that eventually leads to extinction, so be it. However, it's not easy to come with an example. Most species become extinct not because they've evolved in a weird direction but rather because they've failed to evolve fast enough to match changing environment or maybe they were simply outcompeted by other species.

An obvious direction to go in search for examples is sexual selection. Sexual selection can result in run-away evolution like the proverbial peacock's tail, which results in decreased chances of survival for any affected individual. Yet, the run-away process typically ends when it starts decreasing overall fitness of the individual. In other words, once the increased amount of offspring produced by a peacock with extra long tail (peahens prefer cocks with long tails) doesn't compensate for the fact that he is easily caught and eaten by a predator, the tails cease to grow longer.

Yesterday, though, I've found a nice and straightforward example:

Consider, for example, the bacterium Neisseria meningitidis, the cause of often fatal meningitidis. The typical habitat of this bacterium is the human throat, where it causes no adverse symptoms, and is readily transmitted to new hosts. To cause meningitidis, it must first enter the bloodstream, and then cross the blood-brain barrier. In the short term, this is an excellent habitat for the bacteria, but, no matter how rapidly they multiply, bacteria in the cerebrospinal fluid will never infect a new host. […] The explanation is that natural selection within the host produces changes that are advantageous in the short run, but fatal, to the bacterium, in the long run.

The implications to other areas are obvious:

Will humans evolve towards consuming less resources or having less kids so that they don't destroy the planet and survive as a species? Not necessarily. Look at Neisseria meningitidis!

Also, market economy is a self-regulating system very much like evolution. Do we have a guarantee that free-running unregulated market economy is compatible with human survival? No. The fact that it is self-regulating doesn't guarantee anything of the kind. Look at the meningitidis bacterium again!

Martin Sústrik, November 3rd, 2017

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