Man sipping yerba mate in Montevideo, Uruguay. Photo by jorgeloayza via Flickr. CC BY-NC 2.0 DEED. Everywhere you go in Argentina or Uruguay, you’ll see people engaging in an old and much-loved ritual: sipping a hot, slightly bitter infusion of caffeinated leaves from a dried gourd through a filtered metal straw, before passing the gourd to their friends to share. It’s yerba mate, South America’s Indigenous tea with a long and storied history. “Yerba mate” is the common name for Ilex paraguariensis, a shrub native to South America whose dried and cured leaves are brewed in hot water to produce…