It is well-known that most cases of skull elongation are the result of cranial deformation, head flattening, or head binding, in which the skull is intentionally deformed by applying force over a long period of time. It is usually achieved by binding the head between two pieces of wood, or binding in cloth. However, while cranial deformation changes the shape of the skull, it does not alter its volume, weight, or other features that are characteristic of a regular human skull.
The Paracas skulls, however, are different. The cranial volume is up to 25 percent larger and 60 percent heavier than conventional human skulls, meaning they could not have been intentionally deformed through head binding/flattening. They also contain only one parietal plate, rather than two. The fact that the skulls’ features are not the result of cranial deformation means that the cause of the elongation is a mystery, and has been for decades.