Tragedy of the Commons, Over-Population, Cheaters and Evolution


The production of public goods. 

  • Public goods are products manufactured by an individual that can then be utilized by the individual or its neighbors.
  • The public goods produced by the microbes can be used by all, even the individuals who are not themselves producers.
  • Since production comes at a metabolic cost, and thus a cost in fitness, it pays to be a cheater.A cheater is a kind of parasite, living off the public goods producing individuals, without contributing anything to the group.
  • Since the cheaters have higher fitness, the whole group would soon fall into the trap of the tragedy of the commons. The question then is how this is avoided.

The answer is that such a system is regulated by negative frequency-dependent selection. When one kind becomes rare, it gains a fitness advantage, and therefore rebounds to become more frequent again. When cheaters become frequent, the amount of public goods is decreased, and suddenly cheaters are at a disadvantage. This relies on some spatial structure that makes sure that the public goods are on average closer to the non-cheating microbes.

The attentive reader might already have seen the similarity to certain aspects of human society.

Criminals, for example, are cheaters who live off the production of the rest of society. However, society can tolerate some amount of crime, obviously, just as in the microbial world freeloaders can exist at low frequencies.

  • Where the tragedy of the commons in humans has yet to play out, is in the case of population growth, as discussed by Hardin. In many parts of the world, there is no incentive for the individual to be the one that does not have more children.
  • The result is population growth, and if that growth isn’t stopped sooner than later, the result is overexploitation of resources. This is turn leads, as is already all too evident, to the disappearance of many human resources (i.e., other species), and if we’re unlucky, to the eventual disappearance of humans, too.

Incentives needs to be created for all humans not to have many children, such that population growth can be reversed, and the ultimate result of the tragedy of the commons can be avoided.