2023-10-05 カリフォルニア大学バークレー校(UCB)
Four human footprints found in alkali sand at White Sands National Park in New Mexico. The prints date from 23,000 to 21,000 years ago, long before humans were thought to have first entered North America.Courtesy of USGS
◆新たに発表された研究では、針葉樹の花粉(モミ、スギ、松からの75,000個以上の花粉粒子)の放射線年代測定に焦点を当てました。これらの花粉粒子は元のスパイラルディッチグラスの種子が見つかった層から収集され、直接比較ができるようになりました。結果、花粉の年代は放射性炭素年代測定の結果と統計的に同じでした。新しい研究では、この足跡を検証し、3つの独立した証拠が同じ年代を示し、足跡の年代が23,000年から21,000年であることを強力に支持しています。この研究は、アメリカ大陸の入植に関する従来の理論を変える可能性がある重要な発見です。
<関連情報>
- https://news.berkeley.edu/2023/10/05/tests-confirm-humans-tramped-around-north-america-more-than-20-000-years-ago
- https://www.science.org/doi/10.1126/science.adh5007
ホワイトサンズの古代人の足跡に関する論争が、独自の年代推定によって解決される。 Independent age estimates resolve the controversy of ancient human footprints at White Sands
Jeffrey S. Pigati,Kathleen B. Springer,Jeffrey S. Honke,David Wahl,Marie R. Champagne,Susan R. H. Zimmerman,Harrison J. Gray,Vincent L. Santucci,Daniel Odess,David Bustos,and Matthew R. Bennett
Science Published:5 Oct 2023
Editor’s summary
Traditionally, researchers believed that humans arrived in North America around 16,000 to 13,000 years ago. Recently, however, evidence has accumulated supporting a much earlier date. In 2021, fossilized footprints from White Sands National Park in New Mexico were dated to between 20,000 and 23,000 years ago, providing key evidence for earlier occupation, although this finding was controversial. Pigati et al. returned to the White Sands footprints and obtained new dates from multiple, highly reliable sources (see the Perspective by Philippsen). They, too, resolved dates of 20,000 to 23,000 years ago, reconfirming that humans were present far south of the ice sheets during the Last Glacial Maximum. —Sacha Vignieri
Abstract
Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected from the same stratigraphic horizons as those of the Ruppia seeds, along with optically stimulated luminescence ages of sediments from within the human footprint–bearing sequence, to evaluate the veracity of the seed ages. The results show that the chronologic framework originally established for the White Sands footprints is robust and reaffirm that humans were present in North America during the Last Glacial Maximum.
