The brutal facts are that in every generation, each person's genome experiences further mutations, passing on a further reduction in «fitness». (judithcurry.com)
The expansion of the human brain may have involved a snowball effect, in which initial mutations caused further mutations that enhanced the brain even more (newscientist.com)
There's speculation that, with further mutations, the PETase mutant enzyme might even be used to degrade / eat the newer kinds of plastic known as Polyethylene furandicarboxylate or PEF. (bigthink.com)