150: Patrilineal segmentary systems provide a peaceful explanation for the post‑Neolithic Y‑chromosome bottleneck

Guyon L et al., Nature Communications - Forward-time simulations and coalescent inference show that variance in reproductive success among patrilineal descent groups combined with lineal fission can produce the observed post‑Neolithic decline in male effective population size (Y chromosome) without requiring large-scale intermale violence. Key terms: patrilineality, Y-chromosome bottleneck, population genetics, SLiM simulations, social structure.

Study Highlights:
The authors used SLiM forward-time socio-demographic simulations with tree-sequence recording, π-based diversity measures, and Bayesian skyline plots (BEAST) to compare bilateral and patrilineal scenarios with random or lineal fission, group growth variance, migration and modeled violence. They find that variance in reproductive success between patrilineal groups together with lineal fission is sufficient to drive a large reduction in male effective population size while female Ne continues to grow. Violence modeled as high male mortality produces a faster but smaller long-term effect than group-level reproductive variance, and polygyny alone is insufficient to reproduce the observed bottleneck. Timing analyses show that transitions in kinship systems linked to agro-pastoral shifts can produce bottlenecks compatible with archaeological dates.

Conclusion:
A shift toward segmentary patrilineal social organization — characterized by lineal fission and intergroup variance in reproductive success associated with the rise of agro‑pastoralism — can explain the post‑Neolithic Y‑chromosome bottleneck without invoking pervasive ancient violence.

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Article title:
Patrilineal segmentary systems provide a peaceful explanation for the post‑Neolithic Y‑chromosome bottleneck

First author:
Guyon L

Journal:
Nature Communications

DOI:
10.1038/s41467-024-47618-5

Reference:
Guyon L, Guez J, Toupance B, Heyer E, Chaix R. Patrilineal segmentary systems provide a peaceful explanation for the post‑Neolithic Y‑chromosome bottleneck. Nature Communications. 2024;15:3243. doi:10.1038/s41467-024-47618-5

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

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Episode link: https://basebybase.com/episodes/patrilineal-segmentary-systems-and-the-postneolithic-ychromosome-bottleneck

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2025-09-27.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections that explain the Y-chromosome bottleneck, the peaceful patrilineal/segmentary hypothesis, model design (patrilocal residence, patrilineal descent, lineal vs random fission, variance in reproductive success), polygyny tests, simulation methods (SLiM), diversity measures (π-based) and BEAS
- transcript topics: Y-chromosome bottleneck timing and regional variation; patrilineal segmentary systems and peaceful explanation; lineal vs random descent/fission; patrilocal residence and female/male migration; variance in reproductive success and wealth transmission; polygyny tests and their impact on diversity

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 7
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- Post-Neolithic Y-chromosome bottleneck occurred worldwide around 3,000–5,000 years ago; female Ne increased.
- Violence alone cannot explain the Y-chromosome bottleneck; a peaceful explanation is possible.
- Lineal (patrilineal) fission combined with variance in reproductive success reduces male Ne; lineal fission more effective than random fission.
- Polygyny alone reduces male Ne but is insufficient to account for the magnitude of the bottleneck (roughly 4x in a hyper-polygyny model).
- π-based and BEAST skyline plots provide complementary estimates; female-to-male Ne ratio can reach very high values (up to ~29.4 in some scenarios).
- Timing of the bottleneck is compatible with the rise of agro-pastoralism and shifts in kinship systems; explicit violence is not required.

QC result: Pass.