Darwin, earthworms, and the evolution of soil

In 1881 Charles Darwin sent to his publisher John Murray the manuscript of what was to be the last of his many books: “The Formation of Vegetable Mould, Through the Action of Worms, with Observations on their Habits”. Having devoting the last many years of his life to establishing the theory of evolution by natural selection, why did he turn to this seemingly obscure topic and a that book makes no mention of evolution. This last interest of the consummate naturalist Darwin reveals, in fact, an awareness of a microcosm whose internal complexity was clearly established by natural selection. I will show that that organic soils are habitats created by vascular plants starting 400 million years ago, to allow them to exist on the terrestrial surface. They achieve this by: a) facilitating chemical weathering of the rocky substrate; b) providing humus which is a conditioner as well as the nutrient for organisms (including earthworms) which help to maintain the soil. Organic soils are the product of the coveolution of the most diverse ecosystem on the planet.

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