The ancient Romans and Greeks discussed the possibility of other planetary life-forms, and the Copernican Revolution accelerated the belief that we are not alone. Galileo and Kepler and many others discussed the possibility, whilst being cautious not to upset The Church, who condemned the idea as heresy.
Bernard le Bovier de Fontenelle, who wrote "Conversations on the Plurality of Worlds" in 1686, continued with Copernicus' thesis, and offered an explanation on the heliocentric, model of the World, whilst exploring the possibility alien life-forms. A century later, we would be creating crop triangles and burning canals in an attempt to seek attention from another form.
Several 19th Century scientists discussed how we might communicate with extra-terrestrial life forms; Carl Friedrich Gauss, the German mathematician, spoke the 1820s of reflecting sunlight towards the planets with his land surveying invention, the heliotrope, and the search has continued and grown significantly since then. Billions have, and are being spent on initiatives, in an attempt to communicate with our would-be universal cousins.
It is a natural human trait, to seek discovery of new worlds. However, in light of the obvious difficulty human-beings have in living peacefully with their neighbours, and in possessing compassion for others of different colour, language, tradition and religious belief, it poses a question as to whether we are actually ready to embrace another species. How would the world's inhabitants react?
Therefore, the question is, what would we humans do if we were to discover the definite existence of an intelligent life form?