Human Behavioral Ecology
Lecture 19 – Evolution OF Culture
Evolution OF Culture
• Brain evolution, tradeoffs
• Collective Computation and Cumulative Culture
• Sapir-Whorf Hypothesis
• Cultural Transmission and Diffusion
Culture drives evolution of physical phenotype:
Culture: food sharing, language, reciprocity, pair-bonding
Evolution: large brains, bipedality, obstetric problems
Subsistence changes  brain evolution  social complexity
Coevolution of culture,
anatomy, physiology
Human evolution driven by cultural
shifts in subsistence, sociality
Cost of Large Brains
Evidence for fitness tradeoff with larger brains
To be adaptive, payoff has to justify cost of large brains
Brain size responds to selection
Fitness effects
Guppies selected
for large brains had
lower reproductive
success
Kotrschal, A., Rogell, B.,
Bundsen, A., Svensson, B.,
Zajitschek, S., Brännström, I.,
... & Kolm, N. (2013). Artificial
selection on relative brain size
in the guppy reveals costs and
benefits of evolving a larger
brain. Current Biology, 23(2),
168-171.
Benefits of Large Brains
Mammal species introductions vary in establishment success
Large brains aid in adaptation to new environments
Large brained mammals more successful establishing in novel environments
Stronger predictor of success than habitat generalism
Sol, D., Bacher, S., Reader, S. M., & Lefebvre, L. (2008). Brain size predicts the success of mammal species introduced into
novel environments. the american naturalist, 172(S1), S63-S71.
Benefits of Large Brains
Increased foraging efficiency: more food in less time
Frees up time for social activities and “cumulative culture”
Humans forage less than apes
Humans get more food than apes
Lower foraging time +
higher energy intake
 much higher
foraging efficiency
Kraft, T. S., Venkataraman, V. V., Wallace, I. J., Crittenden, A. N., Holowka, N. B., Stieglitz, J., ... & Pontzer, H. (2021). The
energetics of uniquely human subsistence strategies. Science, 374(6575), eabf0130.
Benefits of Large Brains
Increased foraging efficiency: more food in less time
High-skills foraging niche worth the additional energy spent
Extractive foraging
takes more energy
Human Hunter-Gatherers
Higher percentage of Total
Energy Expenditure (TEE)
collecting and processing food
Higher energetic costs but less time
Costs funded by foraging efficiency
Kraft, T. S., Venkataraman, V. V., Wallace, I. J., Crittenden, A. N., Holowka, N. B., Stieglitz, J., ... & Pontzer, H. (2021). The
energetics of uniquely human subsistence strategies. Science, 374(6575), eabf0130.
Sexual Selection and Brain Size
Larger brains in monogamous primates suggest value for
sociality and pair-bonding
Large brains solve complex problems
Especially helpful for social problems
Mate selection, Deception/Detection
Memory, math for reciprocity
Subsistence skills
Language and communication
Cultural transmission
Schillaci, M. A. (2006). Sexual selection and the evolution
of brain size in primates. PLoS One, 1(1), e62.
Collective Brain Mass
Group size (g)  Number of brains
Individual
(g = 1)
Pair (g = 2)
Group (g = 4)
Collective neurons = gN
gN = 4
Collective brain mass
increases exponentially
with population
gN = 8
Large Brain
(N = 2)
gN = 4
Small Brain
(N = 1)
gN = 2
Brain size 
cortical neurons (N)
Hamilton, M. J. (2022). Collective Computation,
Information Flow, and the Emergence of HunterGatherer Small-Worlds. Journal of Social
Computing, 3(1), 18-37.
Collective Brain Mass
Larger groups favor larger brains  high collective brain mass
Individual
(g = 1)
Pair (g = 2)
Group (g = 4)
Collective neurons = gN
gN = 4
Collective brain mass
increases exponentially
with population
gN = 8
Large Brain
(N = 2)
gN = 4
Small Brain
(N = 1)
gN = 2
Brain size 
cortical neurons (N)
Hamilton, M. J. (2022). Collective Computation,
Information Flow, and the Emergence of HunterGatherer Small-Worlds. Journal of Social
Computing, 3(1), 18-37.
Collective Brain Mass
Larger groups favor larger brains  high collective brain mass
Brain size, group size, foraging niche and cooperation co-evolve
Improved foraging
Skills-intensive
foraging niche
Large multimale groups
Selection for
large brains
Selection for
cooperation
Higher benefits to
cooperation
Benefits reflect payoffs
driving coevolution
Higher benefits to
large brains
Increased sociality
Collective Computation – The Phenotypic Gambit
Adaptive Problem: “maximizing fitness by optimizing
information processing given the energy constraints [and
competing tradeoffs] of [surviving in] complex environments”
Importance of information and computational efficiency
• Information processing central to human adaptation
• Social processes depend on collective information processing
• “Parallel Processing” increases efficiency of social systems
• Societies benefit from collective institutions and shared culture
Selection favors sociality and collective action to solve shared problems
Hamilton, M. J. (2021). Collective computation and the emergence of hunter-gatherer small-worlds. bioRxiv.
Collective Computation – The Phenotypic Gambit
Food Sharing: who shares how much of what with whom?
Kinship, residence, family size and reciprocity all matter
Gurven, M. (2004). To give and to give not: The behavioral ecology of human food transfers. Behavioral and Brain Sciences, 27(4), 543-560.
Collective Computation – The Phenotypic Gambit
Phenotypic
Gambit:family
optimizing
foodreciprocity
sharing forallmax
fitness
Kinship, residence,
size and
matter
Selection: alleles for sociality, cultural sharing norms
Older
people give
more
Tradeoff: eat
vs. share
Large families
share less
Reciprocity
Tolerated scrounging?
Neighbors
share more
Neighbors
likely kin
Kin-directed sharing
Gurven, M. (2004). To give and to give not: The behavioral ecology of human food transfers. Behavioral and Brain Sciences, 27(4), 543-560.
Collective Computation – Tinbergen’s 4 Questions
1. Phylogeny: primate brains larger & more neurons for size
Primates (esp. humans) inherit larger, more complex brains
Larger brains for body
More neurons per brain mass
Primates
Mass and density combine to give primates A LOT more neural connections
Hamilton, M. J. (2021). Collective computation and the emergence of hunter-gatherer small-worlds. bioRxiv.
Collective Computation – Tinbergen’s 4 Questions
2. Function: group size allometry with brain size
Large brains adaptive for complex social dynamics
Larger bodies  larger home ranges
Larger home ranges 
Memory requirements for migration
Require more social coordination
Habitat diversity  foraging diversity
Hamilton, M. J. (2021). Collective computation and the emergence of hunter-gatherer small-worlds. bioRxiv.
Collective Computation – Tinbergen’s 4 Questions
3. Causation: metapopulation as hierarchical structure
Population structure adapted to sociality more than to subsistence
Larger bodies  larger home ranges
Consistent group sizes at
different levels of social
organization regardless of
habitat type
Aggregation/disaggregation
and dispersal/intermarriage
aid information flow and
collective problem-solving
Hamilton, M. J. (2021). Collective computation and the emergence of hunter-gatherer small-worlds. bioRxiv.
Collective Computation – Tinbergen’s 4 Questions
4. Ontogeny: similar tradeoffs drive collective solutions
Collective computation as an emergent social property of
the Phenotypic Gambit
All societies face a similar set of problems
•
•
•
•
•
•
•
Subsistence
Shelter
Predator avoidance
Collective defense
Mating
Childrearing
Aging
Collective Computation
Solves common social problems
Reduces unpredictability
Pools skills – division of labor
Pools resources – reciprocity & sharing
Combined “brain power”
Hamilton, M. J. (2021). Collective computation and the emergence of hunter-gatherer small-worlds. bioRxiv.
Collective Computation – The Phenotypic Gambit
Phenotypic Gambit: optimizing time and energy allocation
to maximize individual/inclusive fitness
Tradeoffs: time and energy allocation, quality/quantity, time discounting
Cultural evolution of collective computation
Collective Computation: Phenotypic Gambit at the group level
• Optimizing individual time and energy across individuals
• Pooling resources and information to increase success
• Reducing variance through risk-pooling, food-sharing
Tradeoffs: costs and benefits of individual allocation (~skills, abilities, needs)
Evolution of Cumulative Culture
Cumulative Culture: new strategies build on previous
adaptations  enlarge cultural repertoire
Required for evolution
Novel behaviors can’t spread
Novel behavioral strategies can’t
build on previous adaptations
Boyd, R., & Richerson, P. J. (1996, January). Why culture is common, but cultural evolution is rare.
In Proceedings-British Academy (Vol. 88, pp. 77-94). Oxford University Press Inc..
Evolution of Language
Indo-European Language Family Tree
Language Evolves like biology
•
•
•
•
•
•
Inheritance
Common ancestors
Local adaptation
Geographic variation
Solves Adaptive Problems
Aids cultural transmission
http://web.cn.edu/Kwheeler/IE_Main2_Satem.html
Sapir-Whorf Hypothesis
Language constrains verbal thought via vocabulary & grammar
If we need words to think about something,
then our vocabulary constrains our imagination
According to S-W Hypothesis
Language transmits verbal thoughts,
thoughts reflect our experience, but
language also constrains our ability
to think about our experiences
https://www.pinterest.ca/pin/372602569146831582/
Sapir-Whorf Hypothesis – The Color “Grue”
Language constrains verbal thought via vocabulary & grammar
Languages differ in the number of words they have for colors
Green or Blue?
•Many languages do not have separate
words for green and blue
•Some people who speak the same
language disagree about where the
threshold between colors is
•People more likely to agree it is “grue”
(EITHER blue or green)
“grue”
Sapir-Whorf Hypothesis – Linguistic Relativity
Language constrains verbal thought via vocabulary & grammar
Women: more names for colors
Men: more names for black and brown
Sexual Selection
Female color discernment
aids in mate selection
(e.g., plumage display)
Natural Selection
Male sepia & greyscale
better for night vision and
detecting movement
Frank, J. (1990). Gender differences in color naming: Direct mail order advertisements. American Speech, 65(2), 114-126.
Sapir-Whorf Hypothesis – Linguistic Relativity
Language constrains verbal thought via vocabulary & grammar
Women may use more words to distinguish colors
Bi-Directional Causality
More uses for color names
 more remembered
More names in language
 finer grain applications
https://mastertcloc.unistra.fr/2018/12/17/will-ai-lead-to-the-development-of-anew-form-of-universal-language-and-therefore-to-a-new-conception-of-the-world/
Sapir-Whorf Hypothesis – Linguistic Relativity
Language constrains verbal thought via vocabulary & grammar
Artists may also use more words to distinguish colors
Learning
Experience and
exposure to more
color words increases
vocabulary and allows
detailed distinctions
https://mastertcloc.unistra.fr/2018/12/17/will-ai-lead-to-the-development-of-anew-form-of-universal-language-and-therefore-to-a-new-conception-of-the-world/
https://mastertcloc.unistra.fr/2018/12/17/will-ai-lead-to-the-development-of-anew-form-of-universal-language-and-therefore-to-a-new-conception-of-the-world/
Coevolution – Social, Cultural, Biological
Positive Feedback: Brain capacity  sociolinguistic complexity
Large brains 
Language 
Sociality 
Select for large brains
Steels, L. (2011). Modeling the cultural evolution of language. Physics of life reviews, 8(4), 339-356.
Invention of Agriculture
Agriculture adopted earlier in places with high seasonality
Sedentism began before planting: Granaries  walled cities
Seasonality 
Variable food availability 
Periodic shortages 
Food (seed) storage 
Sedentism 
Seed planting 
domestication
Matranga, A. (2017). The ant and the grasshopper: seasonality and the invention of agriculture.
Cultural Diffusion – Spread of Learned Behaviors
Cultural diffusion of fire ~400,000 BP
Cultural transmission rapidly across the world required
Mobility, communication, tolerance, cooperation
Cultural intromission into
Neandertals 200-300 KYA
Internal Combustion Engine
(1794)
MacDonald, K., Scherjon, F., van Veen, E., Vaesen, K., & Roebroeks, W. (2021). Middle Pleistocene fire use: The first signal of widespread cultural
diffusion in human evolution. Proceedings of the National Academy of Sciences, 118(31).
Cultural Evolution – Micro- vs. MacroMicroevolution: adoption, replication (individual behavior)
Macroevolution: diffusion, persistence (group behavior)
Genetic
Cultural
Mutation Adoption
Micro:
Selection Replication
Radiation Diffusion
Macro:
Speciation Spread
Finkelstein, R. (2008). Introduction to the Compendium and a Military Memetics Overview. A Memetics Compendium, 12-20.
Cultural Transmission
Observation  imitation? (passive transmission)
Communication  adoption? (active transmission)
Cultural Transmission
Spread ~ imitation, adoption
Persistence ~ spread
Cultural Evolution
Novel behaviors spread?
Replaced by new adaptations?
Finkelstein, R. (2008). Introduction to the Compendium and a Military Memetics Overview. A Memetics Compendium, 12-20.
Cultural Evolution ~ Transmission
Transmission routes: genetic, parental, ecological, social
Transmission
Genetic: meiosis  alleles
Parental: maternal effects, imprinting
Habitat: niche construction 
ecological inheritance
Social: teaching, imitation/adoption
Danchin, É., & Wagner, R. H. (2010). Inclusive heritability: combining genetic and non‐genetic information to study animal behavior and
culture. Oikos, 119(2), 210-218.
Evolution of Gill Nets
Gill nets growing larger over time
Gill Net Length
2500
Evolution of Culture
Increasing size of nets
as people imitate
others after observing
success with large nets
2000
1500
1000
500
0
Year
Niche Construction
Changing subsistence
(larger nets) altered
environment (size of fish)
Cultural Coevolution – Selection on Prey Species
Subsistence culture (gill nets)  selection on prey species
Fish life history evolution driven by
human cultural practices (gill net fishing)
Human Culture  Niche Construction
Efficient technology  selection pressure
 life history evolution in prey species
(select for early/small maturity)
Haugen, T. O., & Vøllestad, L. A. (2002). Effects of variable and size-selective gill-net fishing on life-history evolution in grayling. ICES CM.
Cultural Evolution in Animals – Humpback Whales
Song complexity changes over time ~ spread of songs/themes
Revolution
Decreasing complexity ~
adoption/spread of similar songs
Maintains coherent culture
Evolution
Increasing complexity ~
new elements developed
Tests out novel culture
Sinclair, N. C., Ursell, J., South, A., & Rendell, L. (2021). From Beethoven to Beyoncé: Do Changing Aesthetic Cultures Amount to “Cumulative
Cultural Evolution?”. Frontiers in psychology, 12.
Phenotypic Gambit & Cognition
Cognitive demands of real-time behavioral optimization
Cultural evolution of skills, norms, practices
Cultural
Practices
Proximate Outcomes
(e.g., foraging returns)
Behavioral
Strategies
Neural
Circuits
Cause  Effect
Decision  Outcome
Ultimate Outcomes
(e.g., fitness benefits)
Genetic evolution of cognitive apparatus
Memory, learning
Selection on
facultative
decision making
Selection on
alleles underlying
cognition
Brain size, neurology