What? Yeast, the sugar hungry organism that is key to making alcohol (when it eats sugar, it produces alcohol and Carbon Dioxide as a by-product) is naturally occurring, and is found among fruit, and sugary malting barley. This would probably be the link to the first instances of alcohol production, with grapes fermenting on the vine, and barley fermenting when humans first learnt how to make bread. Wild fermented ales tend to have more subtle flavours, with many sours and saisons being created using wild yeast.
Where? Although in the history of beer making, everyone would have used wild yeast, now it is something of a rarity, with some craft brewers using it (Wild Beer, for example). Belgian brewers are particularly well known for using it in their Lambic ales.
When? Fermenting pots were found in Egypt, dating back 4000 years, which gives you an idea of how long wild fermenting has been going for. It is only really in the past few hundred years that we have understood yeast, and how it works (rather than just being able to create the conditions it thrives in).
How? A summery day, where you have time to enjoy the complex and challenging flavours that wild yeast throws up.