"And prior to that time Virgilius was condemned to be burned for asserting the antipodes, or in other words, that the earth was a globe, and habitable in every part where there was land; yet the truth of this is now too well known even to be told." - The Age of Reason
The theory of the antipodes and whether it is agreed to or disagreed to both presumed a spherical Earth. It assumes that the Earth is mostly water and that there might be widely separated land masses where men cannot sail between. If men existed on these separate land masses, then we can dispute over whether or not they were descended from Adam, as we might now dispute whether men - or intelligent life - could exist on a different planet. Paine clearly misunderstood the nature of this dispute. Since Paine wrote long before Washington Irving wrote his fictional account of Columbus being opposed by clerics convinced of a flat earth, it appears that atheists had been actively working up this myth in the 18th, rather than the 19th century as I had previously thought.