Two key features of human sociality are anatomically complex brains with neuron-dense cerebral cortices, and the propensity to form complex social networks with non-kin. Complex brains and complex social networks facilitate flows of fitness-enhancing energy and information at multiple scales of social organization. Here, we consider how these flows interact to shape the emergence of macroscopic regularities in hunter-gatherer macroecology relative to other mammals and non-human primates. Collective computation is the processing of information by complex adaptive systems to generate inferences in order to solve adaptive problems. In hunter-gatherer societies the adaptive problem is to resolve uncertainty in generative models used to predict complex environments in order to maximize inclusive fitness. The macroecological solution is to link complex brains in social networks to form collective brains that perform collective computations. By developing theory and analyzing data, the author shows hunter-gatherers bands of ~16 people, or ~4 co-residing families, form the largest collective brains of any social mammal. Moreover, because individuals, families, and bands interact at multiple time scales, these fission-fusion dynamics lead to the emergence of the macroscopic regularities in hunter-gatherer macroecology we observe in cross-cultural data. These results show how computation is distributed across spatially-extended social networks forming decentralized knowledge systems characteristic of hunter-gatherer societies. The flow of information at scales far beyond daily interactions leads to the emergence of small-worlds where highly clustered local interactions are embedded within much larger, but sparsely connected multilevel metapopulations.
N. Creanza, O. Kolodny, and M. W. Feldman, Cultural evolutionary theory: How culture evolves and why it matters, Proc. Natl. Acad. Sci. USA, vol. 114, no. 30, pp. 7782–7789, 2017.
K. Hill, Life history theory and evolutionary anthropology, Evol. Anthropol. Issues News Rev., vol. 2, no. 3, pp. 78–88, 1993.
F. J. Odling-Smee, K. N. Laland, and M. W. Feldman, Niche construction, Am. Nat., vol. 147, no. 4, pp. 641–648, 1996.
K. N. Laland, F. J. Odling-Smee, and M. W. Feldman, Evolutionary consequences of niche construction and their implications for ecology, Proc. Natl. Acad. Sci. USA, vol. 96, no. 18, pp. 10242–10247, 1999.
K. N. Laland, J. Odling-Smee, and M. W. Feldman, Cultural niche construction and human evolution, J. Evol. Biol., vol. 14, no. 1, pp. 22–33, 2001.
M. Smolla and E. Akçay, Cultural selection shapes network structure, Sci. Adv., vol. 5, no. 8, p. eaaw0609, 2019.
B. Voelkl and R. Noë, The influence of social structure on the propagation of social information in artificial primate groups: A graph-based simulation approach, J. Theor. Biol., vol. 252, no. 1, pp. 77–86, 2008.
J. Becker, D. Brackbill, and D. Centola, Network dynamics of social influence in the wisdom of crowds, Proc. Natl. Acad. Sci. USA, vol. 114, no. 26, pp. E5070–E5076, 2017.
L. M. A. Bettencourt, J. Lobo, D. Helbing, C. Kühnert, and G. B. West, Growth, innovation, scaling, and the pace of life in cities, Proc. Natl. Acad. Sci. USA, vol. 104, no. 17, pp. 7301–7306, 2007.
S. G. Ortman, J. Lobo, and M. E. Smith, Cities: Complexity, theory and history, PLoS One, vol. 15, no. 12, p. e0243621, 2020.
M. J. Hamilton, B. T. Milne, R. S. Walker, and J. H. Brown, Nonlinear scaling of space use in human hunter-gatherers, Proc. Natl. Acad. Sci. USA, vol. 104, no. 11, pp. 4765–4769, 2007.
J. H. Brown, W. R. Burnside, A. D. Davidson, J. P. DeLong, W. C. Dunn, M. J. Hamilton, N. Mercado-Silva, J. C. Nekola, J. G. Okie, W. H. Woodruff, et al., Energetic limits to economic growth, BioScience, vol. 61, no. 1, pp. 19–26, 2011.
V. Romano, S. Lozano, and J. F. L. de Pablo, A multilevel analytical framework for studying cultural evolution in prehistoric hunter-gatherer societies, Biol. Rev., vol. 95, no. 4, pp. 1020–1035, 2020.
M. J. Hamilton, B. T. Milne, R. S. Walker, O. Burger, and J. H. Brown, The complex structure of hunter-gatherer social networks, Proc. Roy. Soc. B Biol. Sci., vol. 274, no. 1622, pp. 2195–2203, 2007.
K. R. Hill, B. M. Wood, J. Baggio, A. M. Hurtado, and R. T. Boyd, Hunter-gatherer inter-band interaction rates: Implications for cumulative culture, PLoS One, vol. 9, no. 7, p. e102806, 2014.
A. E. Page, N. Chaudhary, S. Viguier, M. Dyble, J. Thompson, D. Smith, G. D. Salali, R. Mace, and A. B. Migliano, Hunter-gatherer social networks and reproductive success, Sci. Rep., vol. 7, no. 1, p. 1153, 2017.
C. L. Apicella, F. W. Marlowe, J. H. Fowler, and N. A. Christakis, Social networks and cooperation in hunter-gatherers, Nature, vol. 481, no. 7382, pp. 497–501, 2012.
G. D. Salali, N. Chaudhary, J. Thompson, O. M. Grace, X. M. van der Burgt, M. Dyble, A. E. Page, D. Smith, J. Lewis, R. Mace, et al., Knowledge-sharing networks in hunter-gatherers and the evolution of cumulative culture, Curr. Biol., vol. 26, no. 18, pp. 2516–2521, 2016.
M. Dyble, J. Thompson, D. Smith, G. D. Salali, N. Chaudhary, A. E. Page, L. Vinicuis, R. Mace, and A. B. Migliano, Networks of food sharing reveal the functional significance of multilevel sociality in two hunter-gatherer groups, Curr. Biol., vol. 26, no. 15, pp. 2017–2021, 2016.
P. W. Wiessner, Embers of society: Firelight talk among the Ju/’hoansi bushmen, Proc. Natl. Acad. Sci. USA, vol. 111, no. 39, pp. 14027–14035, 2014.
A. B. Migliano, F. Battiston, S. Viguier, A. E. Page, M. Dyble, R. Schlaepfer, D. Smith, L. Astete, M. Ngales, J. Gomez-Gardenes, et al., Hunter-gatherer multilevel sociality accelerates cumulative cultural evolution, Sci. Adv., vol. 6, no. 9, p. eaax5913, 2020.
E. R. Brush, D. C. Krakauer, and J. C. Flack, Conflicts of interest improve collective computation of adaptive social structures, Sci. Adv., vol. 4, no. 1, p. e1603311, 2018.
B. C. Daniels, C. J. Ellison, D. C. Krakauer, and J. C. Flack, Quantifying collectivity, Curr. Opin. Neurobiol., vol. 37, pp. 106–113, 2016.
K. Friston, The history of the future of the bayesian brain, NeuroImage, vol. 62, no. 2, pp. 1230–1233, 2012.
K. Friston, L. Da Costa, D. Hafner, C. Hesp, and T. Parr, Sophisticated inference, Neural Comput., vol. 33, no. 3, pp. 713–763, 2021.
A. Clark and D. Chalmers, The extended mind, Analysis, vol. 58, no. 1, pp. 7–19, 1998.
H. Kaplan, K. Hill, J. Lancaster, and A. M. Hurtado, A theory of human life history evolution: Diet, intelligence, and longevity, Evol. Anthropol. Issues News Rev., vol. 9, no. 4, pp. 156–185, 2000.
C. C. Grueter, X. G. Qi, D. Zinner, T. Bergman, M. Li, Z. F. Xiang, P. F. Zhu, A. B. Migliano, A. Miller, M. Krützen, et al., Multilevel organisation of animal sociality, Trends Ecol. Evol., vol. 35, no. 9, pp. 834–847, 2020.
M. S. Sugiyama, Oral storytelling as evidence of pedagogy in forager societies, Front. Psychol., vol. 8, p. 471, 2017.
D. Smith, P. Schlaepfer, K. Major, M. Dyble, A. E. Page, J. Thompson, N. Chaudhary, G. D. Salali, R. Mace, L. Astete, et al., Cooperation and the evolution of hunter-gatherer storytelling, Nat. Commun., vol. 8, no. 1, p. 1853, 2017.
D. B. Rose, Dreaming ecology: Beyond the between, Religion&Literature, vol. 40, no. 1, pp. 109–122, 2008.
G. Curran, L. Barwick, M. Turpin, F. Walsh, and M. Laughren, Central Australian aboriginal songs and biocultural knowledge: Evidence from women’s ceremonies relating to edible seeds, J. Ethnobiol., vol. 39, no. 3, pp. 354–370, 2019.
R. P. Norris and D. W. Hamacher, The astronomy of aboriginal Australia, Proc. Int. Astron. Union, vol. 5, no. S260, pp. 39–47, 2009.
N. Tinbergen, On aims and methods of ethology, Zeitschrift Für Tierpsychologie, vol. 20, no. 4, pp. 410–433, 1963.
M. Muthukrishna and J. Henrich, Innovation in the collective brain, Philos. Trans. Roy. Soc. B Biol. Sci., vol. 371, no. 1690, p. 20150192, 2016.
K. E. Jones, J. Bielby, M. Cardillo, S. A. Fritz, J. O’Dell, C. D. L. Orme, K. Safi, W. Sechrest, E. H. Boakes, C. Carbone, et al., Pantheria: A species-level database of life history, ecology, and geography of extant and recently extinct mammals, Ecology, vol. 90, no. 9, p. 2648, 2009.
W. Jetz, C. Carbone, J. Fulford, and J. H. Brown, The scaling of animal space use, Science, vol. 306, no. 5694, pp. 266–268, 2004.
D. A. Kelt and D. H. van Vuren, The ecology and macroecology of mammalian home range area, Am. Nat., vol. 157, no. 6, pp. 637–645, 2001.
R. I. M. Dunbar, P. M. Carron, and S. Shultz, Primate social group sizes exhibit a regular scaling pattern with natural attractors, Biol. Lett., vol. 14, no. 1, p. 20170490, 2018.
N. P. Myhrvold, E. Baldridge, B. Chan, D. Sivam, D. L. Freeman, and S. K. Morgan Ernest, An amniote life-history database to perform comparative analyses with birds, mammals, and reptiles, Ecology, vol. 96, no. 11, p. 3109, 2015.
K. Isler and C. P. van Schaik, The expensive brain: A framework for explaining evolutionary changes in brain size, J. Hum. Evol., vol. 57, no. 4, pp. 392–400, 2009.
D. Sol, S. Bacher, S. M. Reader, and L. Lefebvre, Brain size predicts the success of mammal species introduced into novel environments, Am. Nat., vol. 172, no. S1, pp. S63–S71, 2008.
R. A. Barton and I. Capellini, Maternal investment, life histories, and the costs of brain growth in mammals, Proc. Natl. Acad. Sci. USA, vol. 108, no. 15, pp. 6169–6174, 2011.
J. H. Brown, J. F. Gillooly, A. P. Allen, V. M. Savage, and G. B. West, Toward a metabolic theory of ecology, Ecology, vol. 85, no. 7, pp. 1771–1789, 2004.
R. D. Martin, Relative brain size and basal metabolic rate in terrestrial vertebrates, Nature, vol. 293, no. 5827, pp. 57–60, 1981.
R. S. Walker and M. J. Hamilton, Life-history consequences of density dependence and the evolution of human body size, Curr. Anthropol., vol. 49, no. 1, pp. 115–122, 2008.
O. R. P. Bininda-Emonds, M. Cardillo, K. E. Jones, R. D. E. MacPhee, R. M. D. Beck, R. Grenyer, S. A. Price, R. A. Vos, J. L. Gittleman, and A. Purvis, The delayed rise of present-day mammals, Nature, vol. 446, no. 7135, pp. 507–512, 2007.
D. Bates, D. Sarkar, M. D. Bates, and L. Matrix, The lme4 package, R Package Version, vol. 2, no. 1, p. 74, 2007.
K. Friston, R. A. Adams, L. Perrinet, and M. Breakspear, Perceptions as hypotheses: Saccades as experiments, Front. Psychol., vol. 3, p. 151, 2012.
S. Herculano-Houzel, The remarkable, yet not extraordinary, human brain as a scaled-up primate brain and its associated cost, Proc. Natl. Acad. Sci. USA, vol. 109, no. S1, pp. 10661–10668, 2012.
F. A. C. Azevedo, L. R. B. Carvalho, L. T. Grinberg, J. M. Farfel, R. E. L. Ferretti, R. E. P. Leite, W. J. Filho, R. Lent, and S. Herculano-Houzel, Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain, J. Comp. Neurol., vol. 513, no. 5, pp. 532–541, 2009.
S. Herculano-Houzel, Numbers of neurons as biological correlates of cognitive capability, Curr. Opin. Behav. Sci., vol. 16, pp. 1–7, 2017.
E. L. Charnov, R. Warne, and M. Moses, Lifetime reproductive effort, Am. Nat., vol. 170, no. 6, pp. E129–E142, 2007.
O. Burger, R. Walker, and M. J. Hamilton, Lifetime reproductive effort in humans, Proc. Roy. Soc. B Biol. Sci., vol. 277, no. 1682, pp. 773–777, 2010.
T. Clutton-Brock, Social evolution in mammals, Science, vol. 373, no. 6561, p. eabc9699, 2021.
J. Damuth, Population density and body size in mammals, Nature, vol. 290, no. 5808, pp. 699–700, 1981.
M. Gurven, Reciprocal altruism and food sharing decisions among hiwi and ache hunter-gatherers, Behav. Ecol. Sociobiol., vol. 56, no. 4, pp. 366–380, 2004.
M. J. Hamilton, J. Lobo, E. Rupley, H. Youn, and G. B. West, The ecological and evolutionary energetics of hunter-gatherer residential mobility, Evol. Anthropol. Issues News Rev., vol. 25, no. 3, pp. 124–132, 2016.
J. D. Kilby, S. P. Farrell, and M. J. Hamilton, New investigations at bonfire shelter, Texas examine controversial bison jumps and bone beds, Plains Anthropol., vol. 66, no. 257, pp. 34–57, 2021.
D. Meunier, R. Lambiotte, and E. T. Bullmore, Modular and hierarchically modular organization of brain networks, Front. Neurosci., vol. 4, p. 200, 2010.
M. A. M. de Aguiar, E. A. Newman, M. M. Pires, J. D. Yeakel, C. Boettiger, L. A. Burkle, D. Gravel, P. R. Guimarães Jr, J. L. O’Donnell, T. Poisot, et al., Revealing biases in the sampling of ecological interaction networks, PeerJ, vol. 7, p. e7566, 2019.
B. F. Codding, R. B. Bird, and D. W. Bird, Provisioning offspring and others: Risk-energy trade-offs and gender differences in hunter-gatherer foraging strategies, Proc. Roy. Soc. B Biol. Sci., vol. 278, no. 1717, pp. 2502–2509, 2011.
M. Gurven, To give and to give not: The behavioral ecology of human food transfers, Behav. Brain Sci., vol. 27, no. 4, pp. 543–560, 2004.
D. Smith, M. Dyble, J. Thompson, K. Major, A. E. Page, N. Chaudhary, G. D. Salali, L. Vinicius, A. B. Migliano, and R. Mace, Camp stability predicts patterns of hunter-gatherer cooperation, Roy. Soc. Open Sci., vol. 3, no. 7, p. 160131, 2016.
K. R. Hill, R. S. Walker, M. Božičević, J. Eder, T. Headland, B. Hewlett, A. M. Hurtado, F. Marlowe, P. Wiessner, and B. Wood, Co-residence patterns in hunter-gatherer societies show unique human social structure, Science, vol. 331, no. 6022, pp. 1286–1289, 2011.
M. J. Hamilton, B. Buchanan, and R. S. Walker, Scaling the size, structure, and dynamics of residentially mobile hunter-gatherer camps, Am. Antiquity, vol. 83, no. 4, pp. 701–720, 2018.
L. M. A. Bettencourt, The origins of scaling in cities, Science, vol. 340, no. 6139, pp. 1438–1441, 2013.
M. S. Granovetter, The strength of weak ties, Am. J. Sociol., vol. 78, no. 6, pp. 1360–1380, 1973.
A. B. Migliano, A. E. Page, J. Gómez-Gardeñes, G. D. Salali, S. Viguier, M. Dyble, J. Thompson, N. Chaudhary, D. Smith, J. Strods, et al., Characterization of hunter-gatherer networks and implications for cumulative culture, Nat. Hum. Behav., vol. 1, no. 2, p. 0043, 2017.
R. K. Pan and S. Sinha, Modularity produces small-world networks with dynamical time-scale separation, Europhysics Letters(EPL), vol. 85, no. 6, p. 68006, 2009.
R. N. Carmody and R. W. Wrangham, The energetic significance of cooking, J. Hum. Evol., vol. 57, no. 4, pp. 379–391, 2009.
D. W. Bird, R. B. Bird, B. F. Codding, and D. W. Zeanah, Variability in the organization and size of hunter-gatherer groups: Foragers do not live in small-scale societies, J. Hum. Evol., vol. 131, pp. 96–108, 2019.
R. Walker, K. Hill, H. Kaplan, and G. McMillan, Age-dependency in hunting ability among the ache of eastern paraguay, J. Hum. Evol., vol. 42, no. 6, pp. 639–657, 2002.
I would like to thank Briggs Buchanan, Hyejin Youn, Chris Kempes, Geoffrey West, Jose Lobo, Eric Rupley, Giovanni Petri, Sam Scarpino, and Rob Walker for invaluable discussions of many of the topics raised in this paper, as well as two anonymous reviewers for their thoughtful comments. I would like to thank the Fondation IMéRA − Institut d'études avancées, Aix Marseille Université for funding a residential workshop over the summer of 2016 where many of these issues were first discussed. I also thank Tim A. Kohler, David H. Wolpert, Darcy Bird, and the Santa Fe Institute for organizing and funding this working group.
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