A petroglyph is an image carved or etched into rock. Essentially, a petroglyph is made by scratching away the uppermost surface of a rock to reveal rock of a different color underneath. The petroglyph is among the earliest known forms of art and record-keeping, and prehistoric petroglyphs exist around the globe, some dating back as far as 10,000 years.
The petroglyph was a viable art form for thousands of years. Some Native Americans were still engaging in the practice at the time of the European conquest. A petroglyph can consist of many different types of images. Some are representative in nature, depicting recognizable human and animal figures, while others include geometrical shapes and patterns or what appears to be early systems of writing. Because of their age, it is impossible to interpret most petroglyphs with any degree of certainty.
The mysterious nature of the prehistoric petroglyph has drawn the interest of many scholars, though interpretations are famously divergent. The only consensus is that the petroglyph held a great deal of importance for prehistoric people. Theories about the nature of certain petroglyphs postulate that they are astronomical guides, historical records, or of religious ritual significance.
Especially puzzling is the fact that many petroglyphs show remarkable similarity over vast distances. It is unknown whether this is due to communication and cultural exchange over large distances in prehistoric times or to some sort of innate similarity in the human brain across cultures. Both sides of the argument have passionate advocates.
Some scholars have attempted to translate a petroglyph into modern language. Barry Fell famously claimed to have deciphered petroglyphs in West Virginia as a description of Christ's nativity in an ancient Irish writing system. However, his theory was not well received and has been debunked. Others working with the same petroglyphs came up with completely different translations, suggesting that what the carvings really meant to the people who created them is anyone's guess in the modern era.