This article was originally published with the title “ The Evolution of Paleolithic Art ” in Scientific American Magazine Vol. 218 No. 2 (February 1968), p. 58 doi:10.1038 ...

The two Prehistoric Rock Art Sites in the Côa Valley (Portugal) and Siega Verde (Spain) are located on the banks of the rivers Agueda and Côa, tributaries of the river Douro, documenting continuous ...