<P> The Long Count calendar used by many subsequent Mesoamerican civilizations, as well as the concept of zero, may have been devised by the Olmecs . Because the six artifacts with the earliest Long Count calendar dates were all discovered outside the immediate Maya homeland, it is likely that this calendar predated the Maya and was possibly the invention of the Olmecs . Indeed, three of these six artifacts were found within the Olmec heartland . But an argument against an Olmec origin is the fact that the Olmec civilization had ended by the 4th century BCE, several centuries before the earliest known Long Count date artifact . </P> <P> The Long Count calendar required the use of zero as a place - holder within its vigesimal (base - 20) positional numeral system . A shell glyph---- was used as a zero symbol for these Long Count dates, the second oldest of which, on Stela C at Tres Zapotes, has a date of 32 BCE . This is one of the earliest uses of the zero concept in history . </P> <P> The Olmec are strong candidates for originating the Mesoamerican ballgame so prevalent among later cultures of the region and used for recreational and religious purposes . A dozen rubber balls dating to 1600 BCE or earlier have been found in El Manatí, a bog 10 km (6.2 mi) east of San Lorenzo Tenochtitlan . These balls predate the earliest ballcourt yet discovered at Paso de la Amada, circa 1400 BCE, although there is no certainty that they were used in the ballgame . </P> <P> While the actual ethno - linguistic affiliation of the Olmec remains unknown, various hypotheses have been put forward . For example, in 1968 Michael D. Coe speculated that the Olmec were Mayan predecessors . </P>

What kind of culture did the olmec develop