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Design of life: Why can’t most life forms digest wood?

In “The Lignin Enigma” (Biologic Institute, July 2, 2012), Ann Gauger discusses the fact that lignin (wood) is the most abundant, untapped resource on Earth, given that most life forms can’t digest it.

Wood is composed of a number of complex organic biopolymers that give it its strength, lightness, and flexibility. The most abundant of these, cellulose, is completely digestible by fungi, bacteria and protozoa. Higher organisms like insects and ruminants that get their food from plants rich in cellulose rely on symbiotic relationships with microorganisms in order to digest it. More interesting, though, is the fact that wood’s second most abundant biopolymer, lignin, cannot serve as an energy source for any organism. In fact, the only organisms known to break it down require energy to do so.

Rube shouts in: Dunno about you, but if I wuz that thar tree in the front yard, I’d want that clause in my contract. Rube is dragged off, still shouting. Back to real science.

Gauger continues,

Why should such an abundant resource go unexploited? Darwinian evolution has apparently failed to evolve “a relatively modest innovation—growth on lignin”—over 400 million years, even though many other spectacular innovations—nodulation (a symbiotic relationship between plants and bacteria that permits the fixation of nitrogen), symbiotic pollination systems (between plants, hummingbirds, and bees), and the appearance of carnivorous plants—all appeared during the same time period, and complex biochemical pathways such as C4 photosynthesis have apparently evolved independently many times.

Maybe chipping the trees would not have been in the interests of the development of life? Well, the treehuggers have been telling us that for years.

The curious question it raises is whether, if there is a design of life, some features are not there for a reason. More later.

Abstract here. Paper here.

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2 Responses to Design of life: Why can’t most life forms digest wood?

  1. 1
    englishmaninistanbul

    You know what would really clinch this: A genetically modified lignin-digesting beastie. Just don’t turn it loose, whatever you do…

  2. Some termites can digest cellulose without the aid of bacterial symbionts:

    Hidden cellulases in termites: revision of an old hypothesis

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