Thanks for your interesting and thought-provoking post. I believe there are several reasons that make it healthy for us to be in regular contact with the soil, working the soil with our hands and walking barefoot on the soil regularly. Among those reasons are exposure to soil micro-organisms. Mankind has been in contact with the good earth for millenia and I am certain that we have adapted to benefit from such contact in many ways. The more our lifestyles, diets and healing veer away from nature the fewer natural benefits we get and the more our health tilts towards the unnatural and unhealthy.