Deep in Peru's Acarí Valley lie the ruins of Tambo Viejo, an Inka provincial center where excavations have uncovered tasseled sacrificial llamas and brightly adorned guinea pigs. But save for a few seeds and some stored leaves, evidence of how the Inka used one of their most sacred plants in ritual s remained elusive. Now, archaeologists have discovered coca leaves still stuck in the wool of some sacrificed llamas. ...read more read less