http://www.uncommondescent.com/human-evolution/is-the-human-race-really-only-200-million-years-old/ This is an interesting case. I looked up Hueyatlaco to see what other information was available.
The Wikipedia entry discusses the controversy which has been battled over several decades it appears. The major excavations happened in the 60s NOT the 70s and there were more dating techniques used then cited in the summary above. I suspect the rancour and alienation between the factions will never give us a clear picture of what happened but . . . . .
There are many, many strands of evidence implying a much more recent settlement of the new world than the older dates reported. One site with weird dates should be looked at with suspicion in the same way as you would look at reports of someone getting 200 miles per gallon from their Ford Focus using some new fuel. Worth looking at but treat with extreme caution.
Additionally, speaking from experience and knowing a lot of archaeologists, the chance of sample contamination is significant. My spouse told me about a time they were excavating an English site and were trying to ‘date’ an occupation layer and got results of over 3 million years before present.
If there were several sites that gave similar results then I think a rethink would be in order. But there is this one site. Even good excavators can screw up. AND, against the implication of this post, the results have been discussed and analysed ad nauseum. Even the proponents of the older dates acknowledged the problem:
“The evidence outlined here consistently indicates that the Hueyatlaco site is about 250,000 yr old. We who have worked on geological aspects of the Valsequillo area are painfully aware that so great an age poses an archeological dilemma. If the geological dating is correct, sophisticated stone tools were used at Valsequillo long before analogous tools are though to have been developed in Europe and Asia. Thus, our colleague, Cynthia Irwin-Williams, has criticized the dating methods we have used, and she wishes us to emphasize that an age of 250,000 yr is essentially impossible.” (Steen-McIntyre, Virginia, et al; “Geologic Evidence for Age of Deposits at Hueyatlaco Archeological Site, Valsequillo, Mexico,” Quaternary Research, 16:1, 1981.)
I can’t speak to the “hundreds of other discoveries documented in the scientific literature of the past 150 years” since they are not mentioned but if someone gives me a list I’d be happy to look into them.
But, bottom line. one outlier does not a theory make. Nor does it make a conspiracy.