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Age of Mexican ash with alleged ‘footprints’


Arising from: R. Dalton Nature doi: 10.1038/news050704-4 (2005)10.1038/news050704-4

A report of human footprints preserved in 40,000-year-old volcanic ash near Puebla, Mexico (, was the subject of a press conference that stirred international media attention1. If the claims ( of Gonzalez et al. are valid, prevailing theories about the timing of human migration into the Americas would need significant revision. Here we show by 40Ar/39Ar dating and corroborating palaeomagnetic data that the basaltic tuff on which the purported footprints are found is 1.30±0.03 million years old. We conclude that either hominid migration into the Americas occurred very much earlier than previously believed, or that the features in question were not made by humans on recently erupted ash.

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Figure 1: Analysis of Xalnene ash samples from central Mexico.
Figure 2: Equal area and orthogonal demagnetization diagrams for a specimen of volume 16 cm3.


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Correspondence to Paul R. Renne.

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Renne, P., Feinberg, J., Waters, M. et al. Age of Mexican ash with alleged ‘footprints’. Nature 438, E7–E8 (2005).

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