Monday, September 27, 2021

Footprints In The Mud

Environmental & Science Education, STEM, Paleontology, Earth & Space Science, Archaeology, Nature of Science

Ed Hessler

The journal Science recently reported on evidence of humans in North America during the Last Glacial Maximum (LGM). The full report is behind a membership paywall but a general summary, the abstract, and authors and their affiliations may be read at the link.

The report is on well preserved and detailed footprints "from excavated surfaces in White Sands National Park, New Mexico"...yielding "radiocarbon ages between ~23 and 21 thousand years ago. One of the features of such footprints is that they are "stratigraphically constrained (immobile through time) and bracketed by seed layers."

The BBC's Paul Rincon provides a great story and stunning images (likely left by teenagers, children and occasional adults)). Rincon writes about the uncertainty over "whether stone tools found at an ancient site, are in fact what they appear to be, or are simply rocks broken through some natural process - such as falling from a cliff."

First author Matthew Bennet, Bournemouth University told Rincom ""One of the reasons there is so much debate is that there is a real lack of very firm, unequivocal data points. That's what we think we probably have."

Rincon's reporting includes a discussion of radiocarbon dating in aqueous environments known as the "reservoir effect." The authors think they have accounted for the effect of old carbon recycling which can make sites seem older than they are. The authors also used other supporting evidence. And he has a lovely summary of the historical development of American archaeology in North America which, if this area of science interests you, is worth reading.

Andrea Manica, a geneticists from the University of Cambridge notes that the earliest genetic data is at odds with the new dating (15-16,000 ya) but this suggests "that the initial colonists of the Americas were replaced when the ice corridor formed and another wave of colonists came in."

Of course the scientists wondered what the children were doing there and speculate on a possibility informed by the environment and way of life. 

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