SOURCES — "You're About to Get Domesticated" ============================================ THE HOOK — THE HYPOTHESIS, THE PLANE ------------------------------------ • The self-domestication hypothesis (humans selected against reactive aggression, with the same side effects seen in domestic animals): - Hare, B. (2017). "Survival of the Friendliest: Homo sapiens Evolved via Selection for Prosociality." Annual Review of Psychology 68:155-186. - Wrangham, R.W. (2018). "Two types of aggression in human evolution." PNAS 115(2):245-253. https://doi.org/10.1073/pnas.1713611115 - Wrangham, R. (2019). "The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution." Pantheon. • The airplane comparison (hundreds of strangers sitting calmly for hours; chimpanzees could not): - Hrdy, S.B. (2009). "Mothers and Others: The Evolutionary Origins of Mutual Understanding." Harvard University Press, ch. 1. 1. REACTIVE AGGRESSION — THE MURDER BY THE RIVER ----------------------------------------------- • Reactive (hot) vs proactive (planned) aggression as two separate systems; humans very low on the first, high on the second: - Wrangham 2018, PNAS (above). - Siegel, A. & Victoroff, J. (2009). "Understanding human aggression: New insights from neuroscience." International Journal of Law and Psychiatry 32(4):209-215. (the hot kind is held down by serotonin) https://doi.org/10.1016/j.ijlp.2009.06.001 • Chimpanzee vs hunter-gatherer killing rates (chimps 271 per 100,000 a year, hunter-gatherers at war 164): - Wrangham, R.W., Wilson, M.L., Muller, M.N. (2006). "Comparative rates of violence in chimpanzees and humans." Primates 47:14-26. https://doi.org/10.1007/s10329-005-0140-1 • Collaborative execution of bullies across hunter-gatherer societies, usually with the victim's own relatives taking part so no feud follows: - Boehm, C. (2012). "Moral Origins: The Evolution of Virtue, Altruism, and Shame." Basic Books. - Boehm, C. (2012). "Costs and benefits in hunter-gatherer punishment." Behavioral and Brain Sciences 35(1):19-20. (in 6 of 10 societies looked at closely, a close male relative did the killing) https://doi.org/10.1017/S0140525X11001403 • The Kalahari case (/Twi, a !Kung man who had killed three people; shot with poisoned arrows by several men, then stabbed after death): - Lee, R.B. (1979). "The !Kung San: Men, Women and Work in a Foraging Society." Cambridge University Press, pp. 394-398. (retold in Boehm and Wrangham) - CORRECTION: Lee's account has men AND women stabbing the body afterwards, not only the women. • Why the story starts ~300,000 years ago in Morocco (earliest Homo sapiens, Jebel Irhoud): - Hublin, J.-J. et al. (2017). "New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens." Nature 546:289-292. https://doi.org/10.1038/nature22336 - Wrangham, R. (2021). "Targeted conspiratorial killing, human self-domestication and the evolution of groupishness." Evolutionary Human Sciences 3:e26. (the start needs language to plan a killing) https://doi.org/10.1017/ehs.2021.20 • CORRECTION to "something no other animal has ever done": chimpanzees have been seen ganging up on and killing their own former alpha males. What no other animal has shown is planning it in advance with words. - Kaburu, S.S.K. et al. (2013). "Death of the Alpha: Within-Community Lethal Violence Among Chimpanzees of the Mahale Mountains National Park." American Journal of Primatology 75(8):789-797. https://doi.org/10.1002/ajp.22135 - Pruetz, J.D. et al. (2017). "Intragroup Lethal Aggression in West African Chimpanzees." International Journal of Primatology 38(1):31-57. https://doi.org/10.1007/s10764-016-9942-9 • Rival ideas and limits of the theory: - Wrangham, R.W. (2019). "Hypotheses for the Evolution of Reduced Reactive Aggression in the Context of Human Self-Domestication." Frontiers in Psychology 10:1914. https://doi.org/10.3389/fpsyg.2019.01914 - Gleeson, B.T. & Kushnick, G. (2018). "Female status, food security, and stature sexual dimorphism: Testing mate choice as a mechanism in human self-domestication." American Journal of Physical Anthropology 167(3):458-469. (women choosing gentler men as the driver) https://doi.org/10.1002/ajpa.23642 - Shilton, D. et al. (2020). "Human Social Evolution: Self-Domestication or Self-Control?" Frontiers in Psychology 11:134. https://doi.org/10.3389/fpsyg.2020.00134 2. VULPES VULPES — BELYAEV'S FOXES --------------------------------- • The experiment (Novosibirsk, from 1959; ~130 foxes from a fur farm, 30 males and 100 females; selected only on reaction to a human hand, first tested at one month; "domesticated elite" pups from the 6th generation; floppy ears, white patches, curled tails, shorter snouts and skulls; longer puppy stage; lower stress hormones): - Trut, L.N. (1999). "Early Canid Domestication: The Farm-Fox Experiment." American Scientist 87(2):160-169. https://doi.org/10.1511/1999.2.160 - Trut, L., Oskina, I., Kharlamova, A. (2009). "Animal evolution during domestication: the domesticated fox as a model." BioEssays 31(3):349-360. (how often each trait appeared) https://doi.org/10.1002/bies.200800070 - Dugatkin, L.A. & Trut, L. (2017). "How to Tame a Fox (and Build a Dog)." University of Chicago Press, ch. 1. (the work actually started earlier, quietly, in Estonia; 1959 is when it could be done openly) https://press.uchicago.edu/dam/ucp/books/pdf/course_intro/978-0-226-44418-5_course_intro.pdf - Ptushenko, V.V. & Ramensky, V.E. (2023). "Biologist Nikolai K. Koltzoff: the forgotten genius." Genetics 224(1):iyad033. (genetics banned in Stalin's Soviet Union; why Belyaev started in secret) https://doi.org/10.1093/genetics/iyad033 • Popup "technically artificial selection": the people choosing the breeders is artificial selection; the result is the same kind of change. • Tame fox pups read human gestures as well as dog puppies, without being bred for it: - Hare, B. et al. (2005). "Social cognitive evolution in captive foxes is a correlated by-product of experimental domestication." Current Biology 15(3):226-230. https://doi.org/10.1016/j.cub.2005.01.040 • The genes behind tameness: - Kukekova, A.V. et al. (2018). "Red fox genome assembly identifies genomic regions associated with tame and aggressive behaviours." Nature Ecology & Evolution 2:1479-1491. https://doi.org/10.1038/s41559-018-0611-6 • The argument about how new the dog-like traits really were: - Lord, K.A. et al. (2020). "The History of Farm Foxes Undermines the Animal Domestication Syndrome." Trends in Ecology & Evolution 35(2):125-136. https://doi.org/10.1016/j.tree.2019.10.011 - Trut, L., Kharlamova, A., Herbeck, Y. (2020). "Belyaev's and PEI's Foxes: A Far Cry." Trends in Ecology & Evolution 35(8):649-651. (the reply) https://doi.org/10.1016/j.tree.2020.03.010 3. FEMINIZED FACE — BLOMBOS, THE 1,400 SKULLS --------------------------------------------- • Blombos Cave shell beads, ~75,000 years old: - Henshilwood, C. et al. (2004). "Middle Stone Age Shell Beads from South Africa." Science 304:404. https://doi.org/10.1126/science.1095905 - NOTE: Blombos beads are not the oldest. Beads from Bizmoune Cave, Morocco, are ~142,000 years old: Sehasseh, E.M. et al. (2021). "Early Middle Stone Age personal ornaments from Bizmoune Cave, Essaouira, Morocco." Science Advances 7(39):eabi8620. https://doi.org/10.1126/sciadv.abi8620 • Trading with other groups, moving stone and pigment long distances ~300,000 years ago (Kenya): - Brooks, A.S. et al. (2018). "Long-distance stone transport and pigment use in the earliest Middle Stone Age." Science 360:90-94. https://doi.org/10.1126/science.aao2646 • The skull study ("feminized" faces, brow ridges shrinking, linked to lower testosterone action): - Cieri, R.L., Churchill, S.E., Franciscus, R.G., Tan, J., Hare, B. (2014). "Craniofacial Feminization, Social Tolerance, and the Origins of Behavioral Modernity." Current Anthropology 55(4):419-443. (1,421 skulls; brow down and upper face shorter over time) https://doi.org/10.1086/677209 - University summary: https://www.eurekalert.org/news-releases/626260 - NOTE: only 54 of those skulls are old fossils; the rest are recent people from 30 populations. The trend rests on a handful of very old heads. - NOTE: "big brow = big testosterone" is the short version. The paper's version is less testosterone ACTION (fewer receptors would look the same in the bone). Adult testosterone predicts face shape poorly: Kordsmeyer, T.L. et al. (2019). Adaptive Human Behavior and Physiology 5(2):117-130. https://doi.org/10.1007/s40750-018-0105-4 Whitehouse, A.J.O. et al. (2015). Proceedings of the Royal Society B 282:20151351. (testosterone before birth) https://doi.org/10.1098/rspb.2015.1351 • The rival explanation (brow lost to free up expressive eyebrows, no hormones needed): - Godinho, R.M., Spikins, P., O'Higgins, P. (2018). "Supraorbital morphology and social dynamics in human evolution." Nature Ecology & Evolution 2:956-961. https://doi.org/10.1038/s41559-018-0528-0 • Bonobos show the same pattern without humans involved (where "self-domestication" comes from): - Hare, B., Wobber, V., Wrangham, R. (2012). "The self-domestication hypothesis: evolution of bonobo psychology is due to selection against aggression." Animal Behaviour 83(3):573-585. https://doi.org/10.1016/j.anbehav.2011.12.007 4. BAZ1B — THE NEANDERTHAL AND THE GENE PATCH --------------------------------------------- • Homo sapiens in Bulgaria (Bacho Kiro Cave) about 45,000 years ago, with Neanderthals already there: - Hublin, J.-J. et al. (2020). "Initial Upper Palaeolithic Homo sapiens from Bacho Kiro Cave, Bulgaria." Nature 581:299-302. https://doi.org/10.1038/s41586-020-2259-z - Hajdinjak, M. et al. (2021). "Initial Upper Palaeolithic humans in Europe had recent Neanderthal ancestry." Nature 592:253-257. (those people had a Neanderthal ancestor fewer than six generations back) https://doi.org/10.1038/s41586-021-03335-3 • Neanderthal lineage in Europe for hundreds of thousands of years: - Meyer, M. et al. (2016). "Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins." Nature 531:504-507. (early Neanderthal relatives in Spain, ~430,000 years ago) • Neanderthal brains as big as or bigger than ours; the difference is shape: - Neubauer, S., Hublin, J.-J., Gunz, P. (2018). "The evolution of modern human brain shape." Science Advances 4(1):eaao5961. https://doi.org/10.1126/sciadv.aao5961 • Neanderthal DNA in people today (~2% outside Africa): - Prüfer, K. et al. (2014). "The complete genome sequence of a Neanderthal from the Altai Mountains." Nature 505:43-49. https://doi.org/10.1038/nature12886 • BAZ1B (University of Milan lab; stem cells from people with Williams syndrome and with the duplication; BAZ1B controls neural crest cells that build the face): - Zanella, M. et al. (2019). "Dosage analysis of the 7q11.23 Williams region identifies BAZ1B as a major human gene patterning the modern human face and underlying self-domestication." Science Advances 5(12):eaaw7908. https://doi.org/10.1126/sciadv.aaw7908 • Williams syndrome (missing piece of chromosome 7, 7q11.23; soft facial features, very friendly to strangers): - Kozel, B.A. et al. (2021). "Williams syndrome." Nature Reviews Disease Primers 7:42. https://doi.org/10.1038/s41572-021-00276-z - Mervis, C.B. et al. (2015). "Children with 7q11.23 duplication syndrome: Psychological characteristics." American Journal of Medical Genetics A 167(7):1436-1450. (the opposite, one extra copy: social anxiety, selective mutism) https://doi.org/10.1002/ajmg.a.37071 • Dogs vs wolves in the same patch, friendliest dogs differing the most: - vonHoldt, B.M. et al. (2017). "Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical hypersociability in domestic dogs." Science Advances 3(7):e1700398. https://doi.org/10.1126/sciadv.1700398 - CORRECTION: the dog differences are in BAZ1B's neighbours GTF2I and GTF2IRD1, not in BAZ1B itself. Same patch, different genes. • Limits: the dog result rests on 16 sequenced dogs; BAZ1B is one dial among hundreds, not "the domestication gene": - Sánchez-Villagra, M.R. & van Schaik, C.P. (2019). "Evaluating the self-domestication hypothesis of human evolution." Evolutionary Anthropology 28(3):133-143. https://doi.org/10.1002/evan.21777 • Why modern humans won out over Neanderthals: still unknown (as said in the video). 5. SCLERA — THE WHITES OF YOUR EYES ----------------------------------- • Mammoth hunting in Arizona ~13,000 years ago (Clovis sites of the San Pedro Valley: Murray Springs, Naco, Lehner): - Haynes, C.V. & Huckell, B.B. (eds.) (2007). "Murray Springs: A Clovis Site with Multiple Activity Areas in the San Pedro Valley, Arizona." Anthropological Papers of the University of Arizona 71. • Human eyes: white sclera, the most exposed of all primates; other primates' eyes mostly dark: - Kobayashi, H. & Kohshima, S. (2001). "Unique morphology of the human eye and its adaptive meaning." Journal of Human Evolution 40(5):419-435. https://doi.org/10.1006/jhev.2001.0468 • The cooperative eye hypothesis (babies follow eyes, apes follow heads): - Tomasello, M., Hare, B., Lehmann, H., Call, J. (2007). "Reliance on head versus eyes in the gaze following of great apes and human infants." Journal of Human Evolution 52(3):314-320. https://doi.org/10.1016/j.jhevol.2006.10.001 - Kano, F. et al. (2022). "Experimental evidence that uniformly white sclera enhances the visibility of eye-gaze direction in humans and chimpanzees." eLife 11:e74086. (white sclera boosts gaze reading, even for chimps) https://doi.org/10.7554/eLife.74086 • NOTE: the dark-sclera picture is simpler than the video's version. Many chimps and bonobos have some white sclera, and bonobos' is lighter: - Perea-García, J.O. et al. (2019). PNAS 116(39):19248-19250. https://doi.org/10.1073/pnas.1911410116 - Mearing, A.S. et al. (2022). "The evolutionary drivers of primate scleral coloration." Scientific Reports 12:14119. https://doi.org/10.1038/s41598-022-18275-9 - Clark, I.R. et al. (2023). "White sclera is present in chimpanzees and other mammals." Journal of Human Evolution 176:103322. - Caspar, K.R. et al. (2021). "Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions." Scientific Reports 11:12994. https://doi.org/10.1038/s41598-021-92348-z https://doi.org/10.1016/j.jhevol.2022.103322 • Dogs read human faces and gestures; eyebrow muscles bred into dogs: - NOTE: "wolves mostly can't" depends on upbringing. Hand-raised wolves can follow human cues: Udell, M.A.R., Dorey, N.R., Wynne, C.D.L. (2008). "Wolves outperform dogs in following human social cues." Animal Behaviour 76(6):1767-1773. https://doi.org/10.1016/j.anbehav.2008.07.028 - Kaminski, J. et al. (2019). "Evolution of facial muscle anatomy in dogs." PNAS 116(29):14677-14681. https://doi.org/10.1073/pnas.1820653116 6. CRANIAL CAPACITY — URUK, KUSHIM, THE SHRINKING BRAIN ------------------------------------------------------- • Uruk as the first city, tens of thousands of people, c. 3100 BC: - Algaze, G. (2008). "Ancient Mesopotamia at the Dawn of Civilization: The Evolution of an Urban Landscape." University of Chicago Press. • Kushim, the earliest name on record, on a barley accounting tablet (MS 1717): - Cuneiform Digital Library Initiative, artifact P005340. https://cdli.earth/artifacts/5340 - NOTE: whether "Kushim" is a person's name or a job title is not certain. - CORRECTION: the Kushim tablet is not the British Museum's beer tablet. The British Museum tablet is a different one: daily beer rations for workers, "probably from" Uruk: https://www.britishmuseum.org/collection/object/W_1989-0130-4 - Damerow, P. (2012). "Sumerian Beer: The Origins of Brewing Technology in Ancient Mesopotamia." Cuneiform Digital Library Journal 2012:2. https://cdli.earth/articles/cdlj/2012-2 • Human brain shrinkage in the last ~10,000-20,000 years (men ~157 ml, about a tennis ball; women ~261 ml): - Henneberg, M. (1988). "Decrease of human skull size in the Holocene." Human Biology 60(3):395-405. https://pubmed.ncbi.nlm.nih.gov/3134287/ - DeSilva, J.M. et al. (2021). "When and Why Did Human Brains Decrease in Size? A New Change-Point Analysis and Insights From Brain Evolution in Ants." Frontiers in Ecology and Evolution 9:742639. (proposes ~3,000 years ago) https://doi.org/10.3389/fevo.2021.742639 - Villmoare, B. & Grabowski, M. (2022). "Did the transition to complex societies in the Holocene drive a reduction in brain size?" Frontiers in Ecology and Evolution 10:963568. (disputes the recent timing) https://doi.org/10.3389/fevo.2022.963568 - DeSilva, J.M. et al. (2023). "Human brains have shrunk: the questions are when and why." Frontiers in Ecology and Evolution 11:1191274. https://doi.org/10.3389/fevo.2023.1191274 • Domestic animals have smaller brains than their wild ancestors; sheep ~24%; the biggest losses in senses and fear: - Balcarcel, A.M. et al. (2021). "The mammalian brain under domestication: Discovering patterns after a century of old and new analyses." Proceedings of the Royal Society B 288:20210813. https://doi.org/10.1098/rspb.2021.0813 - CORRECTION: the 24% compares sheep with the European mouflon, not the Asiatic mouflon of Turkey and Iran (the actual wild ancestor). - Ebinger, P. (1974). "A cytoarchitectonic volumetric comparison of brains in wild and domestic sheep." Zeitschrift für Anatomie und Entwicklungsgeschichte 144(3):267-302. https://doi.org/10.1007/BF00522811 - Brusini, I. et al. (2018). "Changes in brain architecture are consistent with altered fear processing in domestic rabbits." PNAS 115(28):7380-7385. https://doi.org/10.1073/pnas.1801024115 - Pohle, A.-K. et al. (2023). "Domestication effect of reduced brain size is reverted when mink become feral." Royal Society Open Science 10(7):230463. https://doi.org/10.1098/rsos.230463 • NOTE: Belyaev's tame foxes' brains did NOT shrink after 60 years: - Hecht, E.E. et al. (2021). "Neuromorphological Changes following Selection for Tameness and Aggression in the Russian Farm-Fox Experiment." Journal of Neuroscience 41(28):6144-6156. https://doi.org/10.1523/JNEUROSCI.3114-20.2021 7. NEOTENY — STILL PLAYING AT 28 -------------------------------- • GTA VI release date, 19 November 2026: Rockstar Games announcement. • Play in adult mammals; domestic animals keep playing into adulthood: - Bradshaw, J.W.S., Pullen, A.J., Rooney, N.J. (2015). "Why do adult dogs 'play'?" Behavioural Processes 110:82-87. https://doi.org/10.1016/j.beproc.2014.09.023 - Himmler, B.T. et al. (2013). "How domestication modulates play behavior: A comparative analysis between wild rats and a laboratory strain of Rattus norvegicus." Journal of Comparative Psychology 127(4):453-464. https://doi.org/10.1037/a0032187 - NOTE: adult chimpanzees do play, rarely: Palagi, E. (2006). "Social play in bonobos and chimpanzees." American Journal of Physical Anthropology 129(3):418-426. https://doi.org/10.1002/ajpa.20289 • Average US video game player age 36 (2024): - Entertainment Software Association (2024), "Essential Facts". https://www.theesa.com/video-games-remain-lifelong-source-of-entertainment-for-190-6-million-americans/ • Neoteny, human faces as juvenile ape faces; human childhood stretched: - Shea, B.T. (1989). "Heterochrony in human evolution: The case for neoteny reconsidered." Yearbook of Physical Anthropology 32:69-101. https://doi.org/10.1002/ajpa.1330320505 - Petanjek, Z. et al. (2011). "Extraordinary neoteny of synaptic spines in the human prefrontal cortex." PNAS 108(32):13281-13286. https://doi.org/10.1073/pnas.1105108108 - Liu, X. et al. (2012). "Extension of cortical synaptic development distinguishes humans from chimpanzees and macaques." Genome Research 22(4):611-622. https://doi.org/10.1101/gr.127324.111 - Smith, T.M. et al. (2007). "Earliest evidence of modern human life history in North African early Homo sapiens." PNAS 104(15):6128-6133. (Jebel Irhoud child: slow growing-up already there) https://doi.org/10.1073/pnas.0700747104 - Smith, T.M. et al. (2010). "Dental evidence for ontogenetic differences between modern humans and Neanderthals." PNAS 107(49):20923-20928. (Neanderthal children grew faster) https://doi.org/10.1073/pnas.1010906107 • Tame foxes stay puppies longer (fear response starts at ~9 weeks instead of ~6): - Trut 1999 (above). - Lord, K. (2013). "A comparison of the sensory development of wolves and dogs." Ethology 119(2):110-120. https://doi.org/10.1111/eth.12044 • "Twelve thousand generations": the best estimate of a human generation is ~26.9 years, so 300,000 years is about 11,000 generations: - Wang, R.J. et al. (2023). "Human generation times across the past 250,000 years." Science Advances 9(1):eabm7047. https://doi.org/10.1126/sciadv.abm7047 • Adult wolves play too, rougher and shorter; play in dogs was likely bred in directly: - Maglieri, V. & Palagi, E. (2024). "Wolves and dogs unleashed: exploring differences and similarities in adult play." International Journal of Play 13(3):277-293. https://doi.org/10.1080/21594937.2024.2388957 OUTRO — IS THE WHOLE IDEA RIGHT? -------------------------------- • One cause behind all the domestication traits (neural crest cells): - Wilkins, A.S., Wrangham, R.W., Fitch, W.T. (2014). "The 'Domestication Syndrome' in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics." Genetics 197(3):795-808. https://doi.org/10.1534/genetics.114.165423 - Johnsson, M., Henriksen, R., Wright, D. (2021). "The neural crest cell hypothesis: no unified explanation for domestication." Genetics 219(1):iyab097. https://doi.org/10.1093/genetics/iyab097 - Reply: https://doi.org/10.1093/genetics/iyab098 • Self-domestication in humans is a well-supported hypothesis, not settled fact. Critics note how little is measured on how fast the human changes happened: - Sánchez-Villagra & van Schaik 2019 (above). • "Every population on Earth shows the same changes": Cieri et al. 2014 (above), skulls from 30 populations worldwide. More, with plain explanations and how sure scientists are about each claim: thepaintprof.com/domesticated