Holocene cultural and climate shifts in NW Africa as inferred from stable isotopes of archeological land snail shells
Bibliographic record
Abstract
Cultural transitions or even societal collapses have often been associated with long-term drought events. Linkages between humans and the environment are best documented in well-constrained archeological records that offer multi-centennial to multi-millennial cultural and paleoclimate data. Two Holocene Capsian sites, Kef Zoura D and Aïn Misteheyia, from NE Algeria document a marked change in subsistence strategies near 8200 cal. yr BP. Radiocarbon dated archeological shells (from 10,300 to 6700 cal. yr BP) of the terrestrial gastropod Helix melanostoma were studied to examine the role of climate change on cultural shifts. Oxygen (δ 18 O) and carbon (δ 13 C) stable isotopes were measured from whole shells and time-series profiles along shell ontogeny to assess average annual paleoclimate and degree of seasonality, respectively. Shell δ 18 O values illustrate that conditions were wetter between 10,300 and 9000 cal. yr BP, coinciding with the ‘African Humid Period’, whereas the environment turned drier at 8000–7600 cal. yr BP, immediately after the 8.2-ka climate event, feasibly comparable in magnitude to the drought episode initiated in 1968 in the Sahel and N Africa. A snail evaporative steady-state flux balance-mixing model suggests that snails at around 8000 years ago precipitated shells under notably lower relative humidity conditions than previous wetter scenarios of the earlier Holocene. The well-known 8.2 ka cold event of the Northern Hemisphere was detected as a drought event that seems to have lasted several centuries in Algeria. The δ 13 C values indicate that snails only consumed and assimilated C 3 plants without noticeable shifts. This study points to multi-millennial humidity fluctuations in NE Algeria, which likely affected the economy and subsistence strategies of prehistoric human groups in the area.
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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) | 0.000 | 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 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".