Kenneth Norman (2005) suggests that Brahmi was devised over a longer period of time predating Ashoka's rule:
"Support for this idea of pre-Ashokan development has been given very recently by the discovery of sherds at Anuradhapura in Sri Lanka, inscribed with small numbers of characters which seem to be Brāhmī. These sherds have been dated, by both Carbon 14 and Thermo-luminescence dating, to pre-Ashokan times, perhaps as much as much as two centuries before Ashoka."
Jack Goody (1987) had similarly suggested that ancient India likely had a "very old culture of writing" along with its oral tradition of composing and transmitting knowledge, because the Vedic literature is too vast, consistent and complex to have been entirely created, memorized, accurately preserved and spread without a written system.