Ardipithecus ramidus ankle provides evidence for African ape-like vertical climbing in the earliest hominins
Bibliographic record
Abstract
The origin of the human lineage was catalyzed by bipedalism, but how this locomotor mode evolved is debated. We investigated the evolutionary context of human bipedalism by analyzing the morphology of the 4.4 million-year-old hominin talus attributed to Ardipithecus ramidus (ARA-VP-6/500-023). Our results demonstrate that ARA-VP-6/500-023 bears similarities to the tali of chimpanzees and gorillas, who are adapted to vertical climbing and terrestrial plantigrade quadrupedalism. Additionally, we identify the presence of derived features in ARA-VP-6/500-023 consistent with previous suggestions of an enhanced push-off mechanism in the foot of Ar. ramidus. Our observations of the human and ape fossil record are inconsistent with recently proposed models of human origins, which envision the last common ancestor of humans and chimpanzees as a generalized arboreal ape. Instead, our results strongly imply that humans evolved from an African ape-like ancestor, which directly narrows the range of explanations for the origin of our lineage.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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 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".