How Soil Is Formed - Soil: Reflections on the Basis of our Existence - page 22

The Very First Soils
How the first soil formed on our planet remains a matter of speculation, but we
do have a few clues. Paracelsus, a sixteenth-century Swiss scientist and alchemist,
made interesting observations of paper-like fragments that he found while hiking
in the Alps. When he put them in water they swelled into a slimy, jelly-like mass
containing a complex microbiological world later compared to the structure of
human cities. In water, this gelatinous material helps prevent the organisms from
being washed away by currents. One could liken it to taking shelter indoors from
a storm. The material also provides insulation, safeguarding the organisms from
excessive temperature swings. Waste products are transported in channels akin to
urban sewers. Remarkably, the organisms in these societies can communicate with
each other. Each bacterium emits signalling molecules whose concentration deter-
mines when the bacteria start producing jelly.
Blue-green bacteria play a critical role in these gelatinous worlds—or biofilms as
we call them today. Paracelsus named them Nostoc because their mucus reminded
him of the symptoms he experienced when he caught a cold. Nostoc has the same
ability as the bacteria in bean and alder roots to bind nitrogen in the air to proteins.
The first soils. Even if we brush our teeth morning and night, bacteria are continually form-
ing new colonies inside our mouths. The oral cavity is a favourable environment, with regular
provision of nutrition and just the right temperature, and teeth are a suitable material to adhere
to. Once the bacteria have attached, they form a protective material in which they embed them-
selves—known as biofilm. A similar process occurs on the roots of plants and on soil particles
where there is good access to nutrients. The very first soils, predating plants and lichens, were
formed by biofilm material gradually gathering in the ground and becoming organic matter