Cyclopia is the most severe form of a rare birth condition in which the developing brain fails to divide into two separate halves. This can also affect facial development, sometimes leaving the baby with a single eye socket in the center of the forehead and severe facial abnormalities. Most babies born with this condition either die before or soon after birth. It is so rare that it occurs in roughly 1 in 100,000 births, so finding physical evidence of it from modern times is difficult, let alone from historical ones.