Geochronology: age of Mexican ash with alleged 'footprints'.
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 attention. 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 1.30+/-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.
Renne
Paul R
PR
Berkeley Geochronology Center, Berkeley, California 94709, USA. prenne@bgc.org
Feinberg
Joshua M
JM
Waters
Michael R
MR
Arroyo-Cabrales
Joaquin
J
Ochoa-Castillo
Patricia
P
Perez-Campa
Mario
M
Knight
Kim B
KB
D005075:Biological Evolution; D004641:Emigration and Immigration / Q000266:history*; D005580:Fossils; D049690:History, Ancient; D006801:Humans; D020407:Internet; D008280:Magnetics; D008800:Mexico; D015203:Reproducibility of Results; D018707:Volcanic Eruptions