Not footprints after all...

The 40,000-year-old footprints from Mexico that I had blogged about earlier turn out to be >1 million year old and hence, are probably not footprints at all:

"The evidence (the British team) has provided in their arguments that these are footprints is not sufficient to convince me they are footprints," said White, who did not contribute to the new work that Renne's group is reporting in Nature. "The evidence Paul has produced by dating basically means that this argument is over, unless indisputable footprints can be found sealed within the ash."

Renne determined the new date using the argon/argon dating technique, which reliably dates rock as young as 2,000 years or as old as 4 billion years. The British-led researchers, however, relied mainly on carbon-14 dates of overlying sediments. Carbon-14 cannot reliably date materials older than about 50,000 years.