Exposure to dirt may be a way to lift mood as well as boost the immune system, UK scientists say.Dirt exposure 'boosts happiness' - BBC News
Lung cancer patients treated with "friendly" bacteria normally found in the soil have anecdotally reported improvements in their quality of life.
Mice exposed to the same bacteria made more of the brain's "happy" chemical serotonin, the Bristol University authors told the journal Neuroscience.
Common antidepressants work by boosting this brain chemical.
As someone with a lifelong love of gardening, this is absolutely not news to me. It's one of the only things I miss, living in New York City.
If the association between soil bacteria and serotonin holds up after experimental testing, though, it raises all sorts of interesting questions.
The human shift to agriculture from a nomadic hunter-gatherer lifestyle took place very recently, in the evolutionary scheme of things - roughly 10,000 years ago, homo sapiens first donned a John Deere cap and squinted at the sky: looks like a good day to plant chickpeas.
In terms of human history, 10,000 years or so is about all we've got of it; the shift to farming slightly predates the development of written language, and of course that's no accident.
In terms of evolutionary pressures, it's the blink of an eye; surely it's not enough time to develop a tendency in human beings to get happy around dirt.