You'd think it might be a bit of a stretch to try and tie Ancient cuisine to delicious Mexican food, but here's an article from National Geographic that might be able to bridge the gap.
I believe that it could be possible that the taco came from Ancient roots. I found in The Frugal Gormet Cooks Three Ancient Cuisines by Jeff Smith, "(The Greeks) developed the 'edible plate,'... by topping the bread with an assortment of 'relishes,' here meaning anything that was put on the bread." This completely sounds like piling ingredients on a tortilla, if you ask me.
To celebrate National Taco Day, Taco Cabana will be giving out FREE breakfast tacos at all their locations Monday, Oct 4 from 7a-9a.
Additionally, Jacala Mexican Restaurant at 606 West Ave, San Antonio, TX 78201is throwing a Taco Day celebration from 7p-9p.
Figure in center is holding a taco.