The speculation about future evolution of bacteria that can digest plastic by using similar enzymes was thought provoking. The actual paper is open access as well and the 'extended pdf' has introductory material that I found interesting.
Collagen is a foundational class of proteins, found in all animals in large amounts. It's weird -- it has an unusual amino acid, hydroxyproline, that is not directly specified in the standard genetic code (instead, it is made by modification of proline after the protein has been synthesized; this conversion requires vitamin C and its failure is one of the pathologies of scurvy).
One version of collagen, Collagen IV, has this weird sulfur-nitrogen double bound that is produced (again, by post-translational modification) using bromine as a reagent, and for this reason bromine (as bromide) in tiny amounts is a necessary trace element in diets. This last fact was only discovered in 2014.
It's interesting what how different types of collagen are influenced, because this might lead to solutions for different collagen disrupting deceases in the human body.
It's hypothesized that a similar story played out for lignin, leading to the majority of the world's coal deposits. In the Carboniferous period ~300 million years ago, plants evolved a class of organic polymers called lignins which were difficult to break down. This lead to a massive accumulation of dead plant matter that nothing could digest. It only ended when fungi evolved the ability to break down lignin.
See the section on coal formation here https://en.wikipedia.org/wiki/Carboniferous
I love this blog article which explains "Why Birds Can Fly Over Mount Everest" from ~first principles starting 450 million years ago, involving the appearance of lignin and the lack of biological processes to break it down. Very funnily and lightly written, just lovely overall: https://nautil.us/why-birds-can-fly-over-mount-everest-23786...
Also "The second theory is that the geographical setting and climate of the Carboniferous were unique in Earth's history: the co-occurrence of the position of the continents across the humid equatorial zone, high biological productivity, and the low-lying, water-logged and slowly subsiding sedimentary basins that allowed the thick accumulation of peat were sufficient to account for the peak in coal formation."
Like in many other cases where alternative theories are proposed, in this case it is likely that both causes have contributed to the coal formation during the Carboniferous.
The peak in coal abundance is so great in comparison with all other times, that a single cause is unlikely to explain it.