<i>Homo sapiens</i> Dispersal and the Peopling of the Americas
Bibliographic record
Abstract
This chapter summarizes the arrival and colonization of Homo sapiens into the Americas. Knowledge for this theme comes from several areas, even though this review focuses on the genetics data. After its emergence in Africa between 200 and 300 kya (thousands of years ago), modern Homo sapiens migrated out of Africa 140–152 kya, hybridizing and admixing with both Neanderthals and Denisovans. Homo sapiens came to America from Asia, through what is now the Bering Strait region, after diverging from its Asian sister groups ~30 kya. Time of entrance in America would be 12.5–18.5 kya, following two alternative but non–mutually exclusive routes: a coastal route following the Pacific Coast, and a “continental” route following the Alberta ice-free corridor. Later migratory waves also occurred, mostly (though not exclusively) affecting circumarctic populations. The number of migratory streams has been estimated from three to five, depending on the authors. Estimates on the size of the founding population vary widely, from an effective population size of ~70 individuals up to 5400 individuals, even though most studies favor values fewer than 1000. This relatively small founder population of Native Americans, associated with a pattern of dispersal and colonization along the continent that favored genetic drift, may explain why some possibly adaptive genetic variants do not show any signature of selection in the Americas. However, evidence of genetic adaptation also suggests a role for natural selection in shaping the genomes of Native Americans, associated with the successful settlement of the diverse environmental landscapes across the Americas.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".