Intriguing finds from San Bartolo in northeastern Guatemala which have been announced over the last six months are overturning old ideas of the Maya Preclassic period as a kind of dark age. The discoveries include murals in vivid colors depicting the Maya mythology of creation and kingship which date to 100 CE, and hieroglyphs (as yet unreadable) a century or two older that attest to an already well-developed writing system. It suggests an earlier origin of the Maya culture than thought and a solid continuity into the Classic period.

This is an interesting article which gives an overview of the significance of the hieroglyphs and murals to our understanding of the way Maya civilization developed : On Ancient Walls, a New Maya Epoch