Abstract
High-elevation environments above 2500 metres above sea level (m.a.s.l.) were among the planet's last frontiers of human colonization. Research on the speed and tempo of this colonization process is active and holds implications for understanding rates of genetic, physiological and cultural adaptation in our species. Permanent occupation of high-elevation environments in the Andes Mountains of South America tentatively began with hunter–gatherers around 9 ka according to current archaeological estimates, though the timing is currently debated. Recent observations on the archaeological site of Soro Mik'aya Patjxa (8.0–6.5 ka), located at 3800 m.a.s.l. in the Andean Altiplano, offer an opportunity to independently test hypotheses for early permanent use of the region. This study observes low oxygen (δ18O) and high carbon (δ13C) isotope values in human bone, long travel distances to low-elevation zones, variable age and sex structure in the human population and an absence of non-local lithic materials. These independent lines of evidence converge to support a model of permanent occupation of high elevations and refute logistical and seasonal use models. The results constitute the strongest empirical support to date for permanent human occupation of the Andean highlands by hunter–gatherers before 7 ka.
Highlights
High-elevation environments above 2500 metres above sea level (m.a.s.l.) pose special challenges for human adaptation [1,2,3]
Least-cost travel analysis indicates that the minimum one-way travel distance between Soro Mik’aya Patjxa and the nearest location on the 2500 m elevation contour would have been 122 km with a travel time estimate of 41 h. This translates to a minimum round-trip distance of 244 km—over three times the 80 km maximum logistical move distance observed among ethnographic hunter–gatherers
The apparent absence of non-local materials at Soro Mik’aya Patjxa and in the Ilave Basin Middle and Late Archaic periods more generally is consistent with year-round use of the high-elevation environment and inconsistent with non-permanent use
Summary
High-elevation environments above 2500 metres above sea level (m.a.s.l.) pose special challenges for human adaptation [1,2,3]. Recent discoveries at the archaeological site of Soro Mik’aya Patjxa located at 3800 m.a.s.l. in the Andean Altiplano of Peru [16] offer an independent case study with which to test multiple novel hypotheses related to high-elevation land-use patterns. Excavations produced the remains of 16 human individuals and abundant lithic artefacts from secure pit-feature contexts dating between 8 and 6.5 ka (table 1) This context is at least 1000 years later than the posited earliest permanent occupation of the highlands, the findings provide a rare opportunity to test multiple previously inaccessible archaeological expectations for early permanent occupation of the highlands by hunter–gatherers. We confront Soro Mik’aya Patjxa with five hypotheses related to human bone chemistry (H1 and H2), geographical positioning (H3), demographic composition (H4) and lithic-material provenance (H5) These multiple tests can inform ongoing debates about high-elevation land-use patterns—debates that partially revolve around interpretive uncertainties associated with few ambiguous lines of archaeological evidence.
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