Mexican Fossilized Impressions - 20,000 Years Old; or 40,000 Years Old; or 1,300,000 Years Old?

Ancient Human Footprints Found in Mexico | Science/AAAS. Geochronological analyses assign wildly divergent dates (20 kyr-1myr) to the fossilized impression. Why? Need there be more fossilized impressions uncovered in rocky outcrops there -- undisturbed by modern-day vehicular traffic -- before science can resolve the disputed claims? Is there an even playing field for studies of the Mexican and African fossils?

There is dispute not only as to the age of the impressions, but also as to whether or not the fossilized impressions are even human footprints. What are alleged to be human footprints occur in what appears to be a pattern for bipedal locomotion, and occur among a plethora of other animal footprints. The dates assigned the fossilized footprints range from 20,000 years old to 1,300,000 years old ! Tim White, who has used the Berkeley lab for dating African fossils, has no doubt that the Berkeley lab has given correct date of about 1.3 million years old; accordingly, he must dispute the human identification that other scientists give the maker of the fossilized impressions. See
http://www.berkeley.edu/news/media/releases/2005/11/30_fp.shtml