[adrian_b]

This has been overlooked, because the methane produced by the newly discovered path is not produced by a normal function of the living beings.

It is caused by an undesirable defect of all living beings. Most of the structure and constituents of the living cells have their origin before large concentrations of free dioxygen have appeared on Earth, and they are easily damaged by it. The living beings that have adapted to live in the presence of dioxygen have acquired many adaptations to protect their sensitive parts from the action of the dioxygen, but these adaptations are not perfect and a little damage may still occur.

Unlike in certain bacteria (the methanogenic archaea), which transform a part of their food into methane to produce energy, this new method of methane generation does not have any advantage for the living beings where it occurs.

On the contrary, it is a byproduct of a process by which the ambient dioxygen destroys a small part of the living matter, which is a loss for the cells where it happens.

This methane is like the soot from an incomplete burning of some organic matter.