Warning: long, philosophical post.
The tragedy of the commons is, roughly, a village with a common green grazing area which all use respectfully, until one or a few overgraze as the cost of this is shared over all the other users. So it becomes necessary to overgraze to stay competitive. Now the commons is really overgrazed and everybody loses; and there’s no point in under-grazing since that won’t make enough difference to fix anything, and is against one’s self interest.
This generalizes to any case where self-interest gets a group into a situation that it cannot get them out of. An example is driving to work. Suppose I can get to work by bus in twenty minutes, but Dave next door drives in ten. So I buy a car, and so does everyone else in our neighbourhood. Now it takes thirty minutes to get to work by car. Going back to the bus is out of the question, that now takes forty minutes due to the extra traffic.
The fact is that a system can get itself into such a predicament, in the more general case. An evolutionary trap is one in which an organism (or a company or an economy or an ecosystem, eh?) evolves into a backwater it cannot easily evolve out of. My favourite example is the spider; apparently its throat passes through its main nerve complex, so it cannot grow larger without having a hole in its head, so to speak. As a compromise, the arachnid sucks the vital fluids of others, allowing as narrow a throat as possible. Apparently spiders with book lungs could, without this throat limitation, have become quite large. But they are in an evolutionary trap.
The marsupials are in a similar trap. The early embryo must crawl from the mother’s womb to the pouch. She does not help it. Therefore its front claws are precocial: they are well developed although the rest of the embryo is still almost a worm. The result of this seems to be that later evolution of the front limbs of marsupials just hasn’t happened. There are no cases of wings, hooves, or grasping hands, just small front feet. The marsupials are in an evolutionary trap.
Large animals who decide who gets to mate via antlers are also in an evolutionary trap: a clever elk who could reroute migration to avoid predators will get thunked out of the gene pool. Horns beats brains here.
An interesting generalization of the idea that an attribute can become a trap is the fact that almost anything that is always present can become a necessity. Parasites become obligate parasites when they give up the ability to synthesize some simple protein because they can always get it from their hosts. Mitochondria have lost many of their original genes because their host cell has decided to make the gene product for them. Evolution prunes a missing function unless that function is provided for some other way, or not necessary, in which case the function generally gets lost. Blind and pigment-less fish who live in light-less caves is an obvious example.
However even something deleterious can become essential. Human sperm must swim through a hostile acid environment. Consequently they have developed a coating that is altered by that experience. Consequently in artificial insemination, sperm must be “capacitated” by being passed through an acid environment.The difficulty has become essential.
Mitochondria behave like bacterial symbionts, which they probably descended from. They fuse and divide all the time. They have their own DNA. They have their own DNA repair system.
The mitochondria in human sperm do not do DNA repairs. This saves energy. It also allows errors to creep into the code. However the egg cell effectively deletes all the mitochondria from the sperm. Thus the competition between sperm has forced a compensatory action on the egg. Once this is done, there is no reason at all for the sperm to do DNA repair in its mitochondria. Thus the exclusion of sperm DNA is now essential.
These specific instances show how “stuff that always happens” or “stuff that always is present” becomes essential. The concept is quite general and applies to cultures, religions, economies, and ecosystems.
I can be forgiven for suggesting that countries with large volumes of drug trade violence have become dependent on this very scourge. It is part of the economy. Money buys influence in a pattern that defends itself as vigorously as the male elk defends his harem. It may not be smart, but it is the way the system works.
I can be forgiven for suggesting that economies with large inequalities have subsystems which enforce and enhance this inequality. One thing I remember from the Unabomber’s Manifesto was his claim that the current system defends, repairs, and enlarges itself. It is so well-developed that it is, in effect, its own evolutionary trap. Self-interest has got the rich into this situation, and it may not be able to get them out of it. If the growing inequality leads to its historically predictable outcome, the rich may well wish they could change that sentence to permit a more pleasant outcome for themselves.