White Sands Footprints, New Mexico
There is quite a bit of emerging evidence that the White Sands Footprints are not 20-22,000 years old but rather much younger (maybe 8-10,000 BP (Before Present). The evidence points to them coming after the last glacial maximum rather than before. In fact most finds in the area date to a maximum of 13,000BP so the 20,000 date is extremely unusual when considering other related finds in the immediate area.
Most of the evidence for the estimated carbon date of 20-22,000 years stems from the pollen & seed collected from the footprints, where a NPS (National Park Service) archaeology team dated the seeds of an aquatic grass (Ruppia cirrhosa) to 20-22,000 years old. What isn't well understood at this time is the extreme fluctuations in the radio carbon sampling due to what is called the hard water effect. Firstly, Ruppia cirrhosa aka Ditchgrass. It is essentially the tumbleweed of aquatic grasses. In seasonal inland brackish lakes, like in the White Sands region where the footprints were sampled, these seeds can form what are called "seed balls" or "lake balls". So the prints, which were found near the perimeter of the lake, contained what they think are portions of seed balls (as well as the pollinae drift from the plant in-flower).
The hard water effect from modern seed, pollen & herbarium specimens suggest fluctuations of up to 10,000 years. This is due to the plant uptaking hard minerals (i.e. very old limestone) from the water (as opposed to leaching carbon from the air). So, naturally, we get crazy results when carbon dating modern herbarium specimens and we know this is true because they've taken additional samples from nearby Salt Creek which, again, shows fluctuations up to 10,000 years for present day, recently harvested samples.
What does this mean for the White Sands footprints? Well, nobody knows for certain yet, but despite all the hype and hoopla surrounding the prints, we can say with some confidence that the evidence supporting their 20,000 radio carbon date is suspect at best.
