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“The label “Green Man”… dates back only to 1939, when it was used by Lady Raglan (wife of the scholar and soldier Major Fitzroy Somerset, 4th Baron Raglan) in her article “The Green Man in Church Architecture”, published in the “Folklore” journal of March 1939.
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The most common… interpretation of the Green Man is that of a pagan nature spirit, a symbol of man’s reliance on and union with nature, a symbol of the underlying life-force, and of the renewed cycle of growth each spring. In this respect, it seems likely that he has evolved from older nature deities such as the Celtic Cernunnos and the Greek Pan and Dionysus.
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Several other ancient cultures also had green deities, often with some features in common with the Green Man. These include: Humbaba, the ancient Sumerian guardian of the cedar forest, as well as Enkidu, the wild man of the forest in Sumerian mythology, both of which date back to at least 3000 BCE; the Egyptian corn-god Osiris, who is often depicted with a green face representing vegetation and rebirth; Attis, a Phrygian god of vegetation and Nature; the Tibetan Buddhist deity Amoghasiddhi; the Hindu demon Kirtimukha; Tlaloc, the Aztec god of rain, fertility and water; and several others. Some of the features incorporated into ancient representations of these gods reappear centuries later in the Green Man. For example, the “Face of Glory” of the Hindu Kirtimukha is usually shown with a mouth issuing leaves, notably missing a lower jaw, and there are several similar representations of a jawless Green Man in Europe.
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Many modern Neo-Paganists and Wiccans, partly as a result of the influential work of Margaret Murray, see the Green Man as a variant of the pagan Horned God, which is in turn a syncretism of several older nature and fertility deities, including the Greek gods Pan and Dionysus, the Roman Silvanus, the Celtic Cernunnos, the Hindu Pashupati, etc (both Dionysus and Cernunnos were sometimes portrayed with hair composed of stylized leaves and vegetation).
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The very fact that images of the Green Man have appeared historically in such disparate and apparently unconnected locations have led some commentators, notably Roweena Pattee Kryder and William Anderson, to suggest that the figure is part of our collective unconscious, and represents a primeval archetype (in Jungian parlance) which is central to our relationship with Nature.
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In the same way, the modern resurgence may have been triggered by the environmental crisis we are currently living through. In its modern revival, in the wake of James Lovelock’s Gaia Hypothesis and the birth of the modern Green movement, the Green Man can be seen as the archetype of the “conservator”, whose brief is to counsel us to take from the environment only what we need to survive and to conserve the rest, and to remind us of our responsibilities for the stewardship of the natural world. A quote from Mike Harding succinctly summarizes this position: “If anything on this poisoned planet gives us hope of renewal it is this simple foliate head that has been there in one form or another since the beginning”.
http://www.greenmanenigma.com/theories.html