As you might guess, this is a highly controversial interpretation; researchers who have grappled and/or continue to grapple with this include Eduard Lartet, Alexander Marshack, Francisco d'Errico and Judith Robinson.
Source
D'Errico, Francesco 2003 The invisible frontier. A multiple species model for the origin of behavioral modernity. Evolutionary Anthropology 12(4):188-202.
D'Errico, Francesco, Christopher S. Henshilwood, and Peter. Nilssen 2001 An engraved bone fragment from c. 70,000 year-old Middle Stone Age levels at Blombos Cave, South Africa; Implications for the origin of symbolism and language. Antiquity 75:309-318.
Marshack, Alexander 1985 A lunar-solar year calendar stick from North America. American Antiquity 50(1):27-51.
Mellars, Paul 2005 The impossible coincidence. A single-species model for the origins of modern human behavior in Europe. Evolutionary Anthropology 14(1):12-27.
This glossary entry is part of the Dictionary of Archaeology.

