DNA study on mummies suggests climate instability drove ancient Peruvians to migrate

"To gain a clearer understanding of early Nasca, Wari and Tiwanaku peoples living in various parts of what is now Peru, the researchers collected DNA samples from 207 mummies found in both coastal and mountainous parts of the region. Mitochondrial analysis and Bayesian modeling indicated that people that had been living near the coast began migrating to the mountains sometime around 640 BC. They also found evidence of a reverse migration as people from the mountains migrated towards the coast around 1200 AD."