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

A report of human footprints preserved in 40,000-year-old volcanic ash near Puebla, Mexico (http://www.royalsoc.ac.uk/exhibit.asp?id=3616&tip=1), was the subject of a press conference that stirred international media attention¹. If the claims (http://www.mexicanfootprints.co.uk) 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 1.300.03 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.

1. Berkeley Geochronology Center, Berkeley, California 94709, USA
2. Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
3. Departments of Anthropology and Geography, and Center for the Study of the First Americans, Texas A&M University, College Station, Texas 77843-4352, USA
4. Laboratório de Arqueozoología, Subdirección de Laboratórios y Apoyo Académico, Instituto Nacionál de Antropología e Historia, CP 06060, México
5. Subdirección de Arqueología, Museo Nacional de Antropología, Reforma y Gandhi s/n, CP 11560, México
6. Proyecto Cuicuilco, Instituto Nacionál de Antropología e Historia, CP 06700, México

Correspondence to: Paul R. Renne^1,2 Email: prenne@bgc.org

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