The high cross underwent some noteworthy transformations over the last 1400 years in Clonmacnois. The most obvious change is that the oldest crosses were decorated on all visible parts, and they did not include any writing. The more recent stones show less artwork, and they all bear some sort of written inscription. This change is attributed to the fact that the Celtic people were largely illiterate before the advent of Christianity in their lands. The Celtic languages were spoken, not written. The earliest high crosses therefore related stories pictographically.
Another important change is the increase in the number of gravestones over time. A steady increase is expected with natural population growth. However, the earliest gravestones were manufactured only for high-ranking individuals. At a certain point in time, gravestone-production became culturally acceptable for all people in the society.
Many elements of the ancient high crosses have remained the same in the modern crosses. For example, ancient and modern bosses, volutes, roofs, and capstones are structurally identical. A difference can be found, though, in the construction of some "bases." Among many of the modern gravestones (of the past two or three centuries), the "base" and the "shaft" collectively transform into a "slab." A "slab" has a broader, flatter surface than does a "shaft." This kind of surface is more amenable to written inscriptions characteristic of the modern gravestones.
