http://www.gardfoods.com/coffee/coffee.coffee.htm A pretty comprehensive, if informal, history of humans' interaction with the coffee plant. People have been chewing coffee berries in Africa for 100,000 years or so. Coffee was definitely growing in Yemen, where it is not native (so must have been planted), in 525 AD.
The list of links in this chapter, often becomes outdated, therefore you might wish to use the excellent Way-Back Machine to find them again: http://www.archive.org/
