The Incas were a great South American civilisation. Until the sixteenth century, they ruled nearly 1 million square kilometers of western South America. Then they disappeared. Not much is known about them because they didn't keep written records. but Reinhard has spent his lift studying them. Before he found the three children on Llullaillaco, he found fifteen other Inca mummies on other mountains. he believes the frozen mummies were human sacrifices to the Inca gods.