Yaxkin was a race of human from planet Yaxkin.
History
People were brought to this planet by Omeyocans to be free from Goa'uld rule. They used the Crystal skull to visit Earth and partake in commerce. This continued until one day the Aztecs came through crystal skull. They took over shipments and the capital Picari. People could not use the crystal skull to get help from other worlds. Coatlicue then arrived in her spaceship and brought with her a Stargate. The people did not know about warfare or how the Goa'uld fought, but they knew about advanced biotechnology, knowledge they would use as weapons.
They unleashed a bioweapon that killed the enemy, except Coatlicue, and that later mutated and killed locals. Yaxkin elders left a message written in a building about the incident and how the virus died out along with the last of their people. A long time later SG-1 and Nicholas Ballard arrived on the planet to investigate it. They found it deserted and the city in ruins, but relised there was no sign of a struggle. After searching they learnt of the Yaxkin's fate. (SG1: "City of the Gods")