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To the Editor: At a height of 8850 m, Mount Everest has long been a magnet to Himalayan mountaineers, and its summit has been reached 2251 times through 2004.¹ Because 130 of those ascents were made without supplemental oxygen,¹ contemporary humans are undoubtedly capable of climbing higher than 8850 m without supplemental oxygen, if a higher summit were available. The upper limit for mountaineers has probably varied over time because atmospheric oxygen concentrations (currently 20.9%) have changed drastically over the past 570 million years.² We simulated how these oxygen shifts would have affected the maximum altitude reachable by hypothetical "paleo-mountaineers."

Methods

To estimate past maximum potential altitudes, we first determined the maximum altitude reachable in today’s atmosphere. West³ calculated that Mount Everest’s summit should be close to the limit of human climbing without supplementary oxygen. Consistent with this, we used 9.0 km as a conservative limit. This is feasible because it . . . [Full Text of this Article]

Raymond B. Huey, PhD
hueyrb@u.washington.edu

Peter D. Ward, PhD
Department of Biology
University of Washington
Seattle