Harvest festivals, usually in the autumn, and rituals offering thanks to divinities, celebrated at various times of the year or in response to single causes, such as the end of a plague or a drought, have existed throughout history. They undoubtedly go back well into pre-history; the sense of a divinity which should be thanked for its benevolence (or propitiated in its anger) may go back even to the time of the Neanderthals. This gives us an early link between German and thanksgiving rituals, since the first sample of a Neanderthal skeleton was found in the valley of the German river Neander. ('-thal', modern '-tal', means 'valley' and is related to English 'dale', as in 'over hill and dale'). (Link to Neanderthal Museum)

Among the ancient harvest festivals in the German-speaking world are those that celebrate the wine-grape harvest. To find out more, search on the term "Weinernte".

Robert Shea's site: German Customs, Traditions, Origins of Holidays

german.about.com: November holidays

Religiöses Brauchtum.de site about Erntedank - compiled by the Archbishophric of Köln

An interesting, often enlightening, sometimes humorous insight into our own culture, including our customs, such as Thanksgiving, can be provided by the reports sent home by visitors to us from other societies. Here is a letter about Thanksgiving as celebrated in a prosperous Oregon suburb. The writer is a teenage German girl who is spending (2000) a year there with a host family.

Many towns and cities in Europe have a "Plague Column" (Pestsäule), which is a monument erected in thanks to God for the end of an attack of the plague, usually the Black Death (bubonic plague). (wikipedia link to article about the Pestsäule in Wien)