Converging evidence constrains Late Pleistocene Bering Land Bridge history
Bibliographic record
Abstract
The Bering Land Bridge was an important biotic corridor and climatic modifier during the Pleistocene (2.58 million to 11,700 thousand years ago [ka]). Understanding when the land bridge was most recently exposed reveals insights into past climate, the modern distribution of plants and animals, and potential human migration into the Americas. While the timing of the most recent flooding of the land bridge has been constrained to during the last deglaciation, the timing of its most recent exposure before the Last Glacial Maximum (LGM, 26.5–19 ka) is less clear. Here, we combine data from three disciplines— paleoceanography, sea level reconstruction, and terrestrial paleogenomics—to constrain the most recent exposure of the Bering Land Bridge to shortly before the LGM, 30–40 kyr later than previously suggested by comparisons of eustatic sea level reconstructions with the modern Bering Strait Sill depth. These results have implications for understanding the timing and nature of human arrival in the Americas and highlight the importance of interdisciplinary collaboration across paleoclimatology and paleoecology for refining Pleistocene environmental history. • Combines interdisciplinary datasets to constrain the timing of the last opening of the Bering Land Bridge. • Illustrates the use of genetics as a paleoproxy for investigating questions of paleogeography. • Provides background information on all proxies to enhance accessibility for a broad, interdisciplinary audience. • Outlines future directions for Bering Land Bridge research and emphasizes the importance of new tools in Quaternary sciences.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".