Coincidence?

At http://phys.org/print308894505.html … Spanish researchers have analysed apinting by Mesolithic hunters with those of the first farming communities, several thousand years later, and found they had one thing in common – the material they used to paint with. The artists from the two periods lived in the same general region and both used iron oxides and pigments that can be found locally. The article in Journal of Archaeological Science 40 (2013) seems to be suggesting the Neolithic populaltion were descended from the Mesolithic hunters, and had adopted farming (or at least the herding of animals). However, if the materials were easily available at the rock shelters they could easily have had no connection with each other.