SOURCES — "Natural Selection Isn't Done With You"
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DOOR ONE — THE WOMB (early pregnancy loss)
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• Estimates of total conception loss range from ~30% to ~50%+ (some estimates higher); most losses occur in the first weeks, before clinical detection. Reviews:
  - Jarvis, G.E. (2016). "Early embryo mortality in natural human reproduction: What the data say." F1000Research 5:2765.
    https://pmc.ncbi.nlm.nih.gov/articles/PMC5443340/
  - Macklon, N.S., Geraedts, J.P., Fauser, B.C. (2002). "Conception to ongoing pregnancy: the 'black box' of early pregnancy loss." Human Reproduction Update 8(4):333-343.
• Majority of early losses linked to chromosomal abnormalities:
  - Hassold, T. & Hunt, P. (2001). "To err (meiotically) is human: the genesis of human aneuploidy." Nature Reviews Genetics 2:280-291.
• Clinically recognized pregnancies: ~10-20% end in miscarriage (ACOG / standard obstetric references).
• Black Death mortality 30-50% of Europe: standard historiography (Benedictow, O.J., "The Black Death 1346-1353: The Complete History", 2004).
• Origin of sexual reproduction / meiosis: ~1-2 billion years ago (eukaryotic origins literature; e.g., Speijer et al. 2015, PNAS, "Sex is a ubiquitous, ancient, and inherent attribute of eukaryotic life").

DOOR TWO — BIRTH / C-SECTION LOOP
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• Obstetrical dilemma (narrow pelvis vs big head), rotational birth, and assisted birth:
  - Washburn, S.L. (1960). "Tools and human evolution." Scientific American 203:63-75. (original obstetrical dilemma)
  - Rosenberg, K. & Trevathan, W. (2002). "Birth, obstetrics and human evolution." BJOG 109(11):1199-1206. (rotational birth, baby emerges facing away, obligate midwifery argument)
  - Trevathan, W. (1987). "Human Birth: An Evolutionary Perspective."
• Rival explanation for 9-month timing (mother's metabolic ceiling, not the pelvis):
  - Dunsworth, H. et al. (2012). "Metabolic hypothesis for human altriciality." PNAS 109(38):15212-15216. (EGG hypothesis; pregnancy runs ~2x basal metabolism, near sustainable human limit)
  - Warrener, A. et al. (2015). "A wider pelvis does not increase locomotor cost in humans." PLOS ONE. (weakens locomotion half of classic dilemma)
• Human newborn altriciality / "born early" compared to other primates:
  - Portmann's secondary altriciality concept; summarized in Dunsworth et al. 2012 above.
• C-section history: ancient salvage operations; Jakob Nufer story (~1500, poorly documented); safe & routine only ~1950 with antibiotics + modern technique:
  - Sewell, J.E. (1993). "Cesarean Section — A Brief History." U.S. National Library of Medicine exhibit.
    https://www.nlm.nih.gov/exhibition/cesarean/
• US C-section rate ~32% (1 in 3): CDC/NCHS births data.
  https://www.cdc.gov/nchs/fastats/delivery.htm
• WHO: medically indicated rate ~10-15%; global rate ~21% and rising:
  WHO statement on caesarean section rates (2015; updated analyses 2021).
• THE C-SECTION FEEDBACK LOOP (core claim):
  - Mitteroecker, P. et al. (2016). "Cliff-edge model of obstetric selection in humans." PNAS 113(51):14680-14685. (fetopelvic disproportion under selection; C-sections predicted to increase mismatch rates ~10-20% relative in ~2 generations)
    https://www.pnas.org/doi/10.1073/pnas.1612410113
  - Mitteroecker, P. et al. (2017). "How evolution changes birth — intergenerational effects of caesarean." (women born by CS for disproportion >2x more likely to develop it themselves)
  - Kuhle, S. et al. (2025). Nova Scotia cohort, n=23,605: women born by CS, adjusted RR 1.36 for delivering by CS. 
  - Evolution, Medicine & Public Health (2025): family clustering of caesarean, daughters RR ~2.1.
• Artificial womb / partial ectogenesis (lambs in "biobag" ~4 weeks):
  - Partridge, E.A. et al. (2017). "An extra-uterine system to physiologically support the extreme premature lamb." Nature Communications 8:15112.

SEXUAL SELECTION SECTION
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• Mammal rule (females choose, males compete; investment logic):
  - Trivers, R. (1972). "Parental investment and sexual selection." (foundational)
  - Clutton-Brock, T. (2007/2009 reviews on sexual selection in mammals.)
• Red deer dimorphism, stags ~200 kg vs hinds ~130 kg; antlers male-only, regrown annually:
  - Clutton-Brock, T., Guinness, F., Albon, S. (1982). "Red Deer: Behaviour and Ecology of Two Sexes." (Isle of Rum long-term study)
• Human body mass dimorphism ~15% (range ~10-20% across populations):
  - Standard figure in the fossil-dimorphism literature (e.g., Plavcan, J.M. 2012, "Sexual size dimorphism, canine dimorphism, and male-male competition in primates," Human Nature 23:45-67.)
  - Concrete modern anchor: US CDC/NHANES mean weights, men 85.6 kg vs women 74.5 kg (~15%).
• Provisioning / pair-bond hypothesis (useless baby → provider choice → pair bonding):
  - Lovejoy, C.O. (1981). "The origin of man." Science 211:341-350.
  - Lovejoy, C.O. (2009). "Reexamining human origins in light of Ardipithecus ramidus." Science 326:74e1-8.
  (Presented as leading hypothesis, not settled; rivals include grandmother provisioning and reduced male-male competition.)
• Long-term vs short-term mate preferences (investment traits dominate long-term pairing):
  - Buss, D.M. (1989). "Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures." Behavioral and Brain Sciences 12:1-49.
  - Ovulatory-shift "bad boy" effects largely failed pre-registered replication (e.g., Jones, B.C. et al. 2018, Psychological Science; Gangestad follow-ups).
• FOSSIL EVIDENCE — canine reduction & body-size dimorphism collapse:
  - Suwa, G. et al. (2021). "Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like." PNAS 118(49):e2116630118. (>6-Myr fossil canine dataset; Ardi dimorphism weaker than bonobo; honing complex lost in all earliest hominins; female-choice mechanism discussed)
    https://www.pnas.org/doi/10.1073/pnas.2116630118
  - White, T.D. et al. (2015). "Neither chimpanzee nor human, Ardipithecus reveals the surprising ancestry of both." PNAS 112(16):4877-4884. (male canines "feminized")
  - Brunet, M. et al. (2002). "A new hominid from the Upper Miocene of Chad, Central Africa." Nature 418:145-151. (Sahelanthropus, ~6.8-7.2 Ma)
  - Australopithecus ~50% male-heavier estimates: classic reconstructions (e.g., McHenry, H.M. 1992, "Body size and proportions in early hominids," AJPA 87:407-431); note active debate, some argue lower (Reno et al. 2003, PNAS).
  - Homo erectus dimorphism ≈ modern (~15-20%): McHenry & Coffing (2000), "Australopithecus to Homo," Annual Review of Anthropology.

MODERN SELECTION — THE RECEIPTS
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• NETHERLANDS HEIGHT STUDY:
  - Stulp, G., Barrett, L., Tropf, F., Mills, M. (2015). "Does natural selection favour taller stature among the tallest people on earth?" Proceedings of the Royal Society B 282:20150211. (LifeLines, n=94,516; taller men more children, up to ~0.24 extra; also less likely childless)
    https://royalsocietypublishing.org/doi/10.1098/rspb.2015.0211
  - Honest correction: Stulp et al. 2023 simulation — selection explains only a small fraction (~0.07-0.36 cm) of the ~20 cm Dutch height rise; nutrition dominates.
  - US counterpoint: Stulp et al. 2012 (Wisconsin sample) — average-height men had most children.
• FRAMINGHAM SELECTION STUDY:
  - Byars, S.G., Ewbank, D., Govindaraju, D.R., Stearns, S.C. (2010). "Natural selection in a contemporary human population." PNAS 107(suppl 1):1787-1792. (women; selection gradients: lower cholesterol, lower systolic BP, shorter, heavier, earlier first birth, later menopause; tiny per-generation effects, e.g., ~1 month shifts; projections ~400 yrs)
    https://www.pnas.org/doi/10.1073/pnas.0906199106
  - Stearns quote ("just plain wrong"): Yale News, Oct 19 2009.
    https://news.yale.edu/2009/10/19/evolution-s-path-may-lead-shorter-stouter-women-who-give-birth-earlier
• UK BIOBANK GENOMIC SELECTION:
  - Sanjak, J.S. et al. (2018). "Evidence of directional and stabilizing selection in contemporary humans." PNAS 115(1):151-156. (n≈409,000; selection on age at first birth, BMI-linked variants)
    https://www.pnas.org/doi/10.1073/pnas.1707227114
• MEETING ONLINE AS #1 VENUE:
  - Rosenfeld, M., Thomas, R., Hausen, S. (2019). "Disintermediating your friends: How online dating in the United States displaces other ways of meeting." PNAS 116(36):17753-17758. (online = most common way US couples meet, crossover ~2017)
    https://www.pnas.org/doi/10.1073/pnas.1908630117
• NORDIC CHILDLESSNESS REGISTERS (the 1-in-4 filter):
  - Jalovaara, M. et al. (2019). "Education, gender, and cohort fertility in the Nordic countries." European Journal of Population 35:563-586. (male childlessness levels & education gradients)
  - Golovina, K. et al. (2023). "Birth cohort changes in fertility ideals..." / register studies of 2.5M Finns & Swedes incl. childlessness-disease associations:
    Tanskanen, A.O. et al. (2025)/Nature Human Behaviour (2023): early-life disease (esp. mental-behavioural) strongly associated with childlessness, effect runs through singlehood; ~25% of men, ~20% of women childless.
  - Norway arc 14% (1985) → ~23-25% (2010s), women 10% → 13%: Statistics Norway (SSB) cohort fertility reports; Kravdal, Ø. work.
  - Finland 19% (1990) → 29% (2022): Statistics Finland; Rotkirch/Väestöliitto (Family Federation of Finland) reports.
  - Rural male surplus & childlessness (geography factor): Finnish register study, Population Studies (2025), partner-market sex ratios.
  (NOTE: registers sort by partnership/education/health/geography — NOT by physical traits. Never claim "the filter selects for X trait.")

FRAMING / DEFINITIONS
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• Sexual selection as subset of natural selection (modern view) vs Darwin's two-force framing:
  - Darwin, C. (1871). "The Descent of Man, and Selection in Relation to Sex."
  - Standard modern treatment: any current evolution textbook (e.g., Futuyma & Kirkpatrick, "Evolution").
• Newborn palmar grasp / body-weight hanging:
  - Robinson, L. (1891). "Darwinism in the nursery." Nineteenth Century. (classic demonstrations)
  - Modern reflex literature: palmar grasp present at birth, fades ~3-6 months.
• Human brain size decline over last ~10,000 years (pocket fact, not in VO):
  - DeSilva, J. et al. (2021). Frontiers in Ecology and Evolution.