Why did it take single celled organisms so long to evolve to break down dead trees

When trees first appeared on earth, it took tens of millions of years for microbes to evolve the enzymes necessary to start breaking down the trees. This GQ is based on the assumption (If I’m wrong, correct me but this is my understanding) that after trees evolved around 400 mya, it took 50-60 million more years for microbes to evolve to decompose them.

So in todays era where microbes seem to be able to evolve antibiotic resistance in 30 years, why would it take 50 million years for microbes to evolve the ability to break down the components of plants and trees? It seems like a long time for microbes to evolve to take advantage of a massive food source. There are already microbes that can break down manmade plastics and those are only a hundred years old.

BTW bacterial resistance to our antibiotics isn’t strictly evolution, the parasitic plasmids have already evolved before, and the bacteria merely become infected with the resistance providing plasmid (effectively its a parasite… a life form that lives in another. its often called symbiotic… which means two life forms tied together, depending on each other… )
If the 40 my is roughly correct, then it may well be that it was due to incremental process of evolution. You see, evolution is survival of the fitest, and it makes no sense that a small single cell life form suddenly evolves a huge enzyme able to break down the huge polymers eg cellulose…lignin…

makes enzymes that are very very weak at breaking down cellulose… the single cell life form doesn’t “know” that in 40 million years, its ancestors will thank them for the attempt !.

See cellulose is huge, because its the polymer of glucose…
The enzymes to break down sugars into glucose or ATP can’t handle cellulose.
How would a life form’s random genetic changes work to change a small enzyme that attacks lactose (For example) to one that attacks cellulose ? Its like putting a breading pair of short haired dogs in the desert and expecting them to make puppies that eat sand and don’t drink. Its just too much of a change to occur in one step.

What makes sense is that the random genetic changes only caused the enzyme to change a little in capability… They only grow the ability to attack slightly larger sugars in any one genetic change… The evolutionary advantage was that the fungi or bacteria could make more advantage of the various cell wall molecules, and the precursors found in sap, in the leaves and the phylum,and so on, and so the one with the larger enzyme has yhe advantange… it just can’t happen overnight.

Never heard of this theory! Can you give a cite?
I wonder what the evidence for it could possibly be – can you reliably identify signs of biodegradation or the decomposing organisms themselves in fossil wood?

Interesting question.

Man, there must have been a buttload of dead wood piled up there for awhile.

The first trees evolved something like 350-450 mya, so life forms that could decompose the trees didn’t exist until 300 mya leaving a 50-150 million year gap where dead trees just built up (and became fossil fuels or caused massive forest fires).

These types of questions rarely have factual answers, but if the microbes were doing perfectly well eating whatever it was they were eating, why should they quickly evolve to eat something new? In the case of antibiotics, it’s is absolutely a matter of survival. It only takes a tiny, tiny % to start an entirely new strain. Further, the mechanism for breaking down cellulose could be more complex than that of fighting off an antibiotic.

The article doesn’t say that - that’s an oversimplification. The article is talking about just one component of wood, lignin. Cellulose is a more important component. Cellulose is also tough to break down, but a variety of organisms including bacteria and protozoa can do it. I’m not sure when this ability first evolved but it was probably long before lignin.

Wood and trees weren’t completely immune from decomposition before the evolution of white-rot fungi. (Note these are multicellular, not “single celled organisms” as in the OP.) The fungi just sped up the process.

And coal deposition didn’t cease afterward. There are plenty of massive coal beds that were laid down in the Cretaceous and later.

It absolutely IS evolution; it’s just evolution by a slightly different mechanism. Not all evolution requires de novo creation of novel genes.

In fact, the mechanism for breaking down both cellulose and lignin are quite complex, which is unsurprising given the complexity of these molecules. Cellulose is at least a relatively simple polysaccharide that will break down by hydrolysis in a mild in polar solution, which you can observe by putting a piece of uncoated paper in water for a few hours where it will basically revert to pulp. Lignin, on the other hand, is a complex polyphenolic macromolecule with complex cross-linkages. It is not soluble in water or simple alcohols, hence why hardwoods are such a good material for storing or protecting from water, especially when treated with creosote or another agent that inhibits fungal growth. The degradation of lignin structures requires not only a complex enzyme (typically lignin perioxidase) but also other metabolites and an energetic fuel (in this case, hydrogen perioxide) which also has to be produced by the organism breaking down lignin. We don’t really even have a comprehensive understanding of lignin biodegradation at a detail level. As far as I’m aware, plants which use lignin do not produce enzymes to break it down, hence why trees continue growing upward and outward indefinitely (unlike animals which are in a constant state of breaking down and replacing many tissues on an ongoing basis). There is a lot of energy stored in the macropolymers that make up lignin, but the material is very robust. Once might as well ask why organisms evolved to directly consume coal or petroleum haven’t spread across the planet.

Antimicrobial resistance, on the other hand, is a relatively straightforward manner of changing the epitrope by random mutation which prevents an antibody or lymphocyte from binding to it. Because this is often encoded in plasmids or fungible codon sequences it can be easily shared by lateral gene transfer, hence why populations of antibiotic resistant bacteria can spread so prolifically. It only takes a small colony of successful (e.g. resistant) microbes to populate a host organism and then spread to others by any number of vectors, and that spread, as with viral infections, will be geometric progression until it hits some limiting factor (no more hosts, containment of the population, natural resistance, et cetera.) Bacteria become resistant to antibiotics, or more specifically, to the response of the immune system, because that’s what they do; they grow and mutate as fast as resources will permit, and occasionally those mutations will impart resistance.


That’s not what we mean by “antibiotic resistance”. Antibiotics are small molecule drugs, and resistance is conferred by the expression of enzymes that break down the drug, or pump it out of the cell, or by altering the target molecule that the drug interferes with. Nothing to do with avoiding the immune system.

This is incorrect - paper pulp is still cellulose fibres, no hydrolysis of the cellulose has occurred. It takes a lot more than water tobreak down cellulose, or everything would be doing it.

The trees themselves evolved along with these fungi. As long as there’s an exploitable niche, something will exploit it.

A study just published in PNAS reports that there was no lag between evolution of lignin synthesis (and hence development of large woody trees) and fungal ability to break down said lignin.

Delayed fungal evolution did not cause the Paleozoic peak in coal production

And just to re-iterate, most fungi are not single celled organisms, especially not the ones that break down dead trees.