why can't non-biodegradable substances be degraded?
If evolution provides survival benefits, then why don't the decomposers develop an enzyme which degrades the plastics,metal pieces,etc as its been quite some time we have been dumping the plastics and metals in the pits?
Non biodegradable substances are made up of such materials which cannot break down easily or cannot be degraded by the enzymes secreted by the microorganisms. They are mostly inorganic substances like plastics and metals. So it takes long time (more than 500 years) to degrade non biodegradable substances.
Evolution is a totally natural process governed by nature. If nature supports, evolution may result in producing microorganism degrading non biodegradable substances. Evolution occurs as a result of continuous environmental changes taking place for thousands and millions of years.