Pleistocene Paw, Hoof, and Footprints in New Mexico (redux)

I already wrote an article with this title 2 years ago, but a minor disaster last week inspired me to rewrite it. In the original article I wrote the fossilized human footprints found at White Sands National Park were at least 11,000 years old. A new study published last year determined the footprints were between 23,000 years-21,000 years old. I tried to edit in a note to the old article explaining the results of the new study, and some kind of glitch erased the last 2 paragraphs and the image I used for the original article. I could look for the old handwritten first draft in a stack of old notebooks I keep in a dusty, old, cardboard box, then retype it, but I decided to start all over and rewrite it completely.

During the late Pleistocene climate patterns were much different in the American Southwest than they are today. The region enjoyed higher rainfall and a cooler more temperate climate, resulting in abundant lakes. Lake Otero, now a completely dry lakebed, was filled with water then and surrounded with lush prairie and scattered trees. A drier climate phase struck, and the lake began to recede, leaving a muddy shoreline where many species of mammals left trackways, including humans, mammoths, camels, bison, Harlan’s ground sloths, saber-toothed cats, giant lions, and dire wolves. Some of the human trackways crisscross those of a ground sloth, and it appears as if the sloth paused and stood, so the animal could better detect the human scent. 61 fossilized human footprints have been found here, and they are mostly of teenagers and children. Apparently, the teenagers were going back and forth, as if they were carrying objects. Children appear to be playing. Scientists hypothesize the adults were fishing and/or collecting edible aquatic plants, and the teens were carrying the items to a camp (not yet found by archaeologists). One teenager was babysitting a toddler and carrying it around.

Human trackways at White Sands National Park in New Mexico. Some scientists estimate these footprints are about 21,000 years old. Human trackways are interspersed with the prints of Pleistocene megafauna.

Artist’s rendition of White Sands National Park 21,000 years ago. Image is a courtesy of the National Park Service.

Of course, fossilized footprints can’t be radiocarbon dated, so how did scientists date the trackways? They radiocarbon dated the ditch grass (Ruppia cirrhosa) seeds found in sediment above and below where the trackways are located. They determined the trackways are between 23,000 years BP-21,000 years BP. This evidence contradicts mainstream archaeologists who believe humans didn’t arrive in North America until about 14,000 years ago.

Diagram showing how the conclusions by the above discussed study could be wrong. Gary Haynes believes wind erosion redeposited older sediment over younger sediment or simply displaced younger sediment so 21,000-year-old ditch grass seeds were on the surface when men and megafauna walked in the area 13,000 years ago. Image from the below reference (Haynes 2022).

Gary Haynes, a renowned archaeologist, casts doubt on the purported age of the trackways. In an article he published in the journal PaleoAmerica, he points out 3 factors that could cause the scientists to reach misleading conclusions about the age of the trackways. The presence of hardwater in an environment causes radiocarbon dates to be older than they actually are. The scientists who dated the trackways were aware of this but think this isn’t a problem because local water is currently not hard. However, Haynes points out they didn’t analyze modern ditch grass to see if it absorbs a greater concentration of hard water than is found in the environment. Another factor that could cause misleading dates is redeposition of sandy sediment by wind. One study of a stratigraphic column in the area nearby found roughly half of the dates were out of order with older sediment on top of younger sediment and alternating with it. Haynes thinks the stratigraphic column in the region where the trackways are found date to between 15,000 years BP-11,000 years BP, dates consistent with when the Clovis culture was known to occur in North America. Finally, he thinks the trackways were made 13,000 years ago, but the exposed sediment where the humans and animals walked happened to be older due to wind redeposition. In other words wind blew the younger sediment away, and people and animals were walking on old sediment.

M. Bennett is the lead author of the study determining the trackways were 21,000 years old. His response to Haynes’s alternative explanation was short and rather obtuse. He believes it was unlikely redeposition of windblown sand occurred, but he offers no explanation why. He also stated the trackways couldn’t be of Holocene age because the human trackways were interspersed with Pleistocene megafauna trackways, and Pleistocene megafauna were extinct by the Holocene (beginning about 11,000 years ago). However, Haynes merely quoted another study that mentioned the trackways being of Holocene age was just 1 of 3 possibilities. Bennett didn’t even address Haynes’s belief that the trackways date to 13,000 years BP when Pleistocene megafauna still roamed the region.

References:

Bennett, M. , et. al.

“Evidence of Humans in North America during the Last Glacial Maximum”

Science 373 6562 2021

Haynes, G.

“Evidence for Humans at White Sands National Park during the Last Glacial Maximum could be for Clovis People ~13,000 years ago”

PaloeAmerica March 2022