In a recent thread the old Hueyatlaco site came up and the old claim of conspiracy in supressing its results.
Yep there was a lot of politics and gnashing of teeth for a number of years........
There was a great gulf of time in between archaeological excavations at Valsequillo, specifically Hueyatlaco, the highest site, and the most
productive on several levels, including an in situ technological transition.
The last year an archaeologist dug there was 1966.
In 1973, Hal Malde, the lead geologist, got permission from Jose Lorenzo to do a geological trench, but no archaeology.
It was the results of this expedition that became the 1981 QR paper, eight years later. In that paper the claim of an age of 250,000 years was made
for the site.
The next time there was any kind of excavation at Hueyatlaco was 2001, which was inspired by Marshall Payn, an outsider (MIT engineering graduate,
past president of the Epigraphic Society), in conjunction with UNAM and INAH. There was a 35-year gulf between archaeological investigations, and none
after 1973.
Since 2001, all hell has broken out at Valsequillo. We have three geological models being postulated for the area. 40,000y, 250,000y, and 1,300,000y.
Sometimes science go down a wrong path because of human ego, politics or whatever-but it often gets back on the path sooner or later.
So what is important about this?
Human artifacts associated with those dates...
There is a conference to be held soon to discuss those and I can recommend a book on the subject
A new book on the subject 
