The conversation, in brief.
In this episode of the podcast, hosts Dave Pietraszewski and David Pinsof are joined by guest co-host Christina Moya and guest Rob Boyd to discuss cultural evolution, evolutionary psychology, and the historical foundations of Darwinian theory. The participants explore how cultural transmission differs from genetic inheritance, examining human cognitive adaptations, brain modularity, social norms, and morality. Boyd reflects on his decades of research, sharing personal anecdotes about John Maynard Smith and discussing fieldwork in Fiji. The conversation also addresses methodological challenges in modeling, the impact of Pleistocene climate fluctuations on human cooperation, and how theoretical views on cultural group selection and conformist transmission have evolved over time.
Through the conversation.
22 sections010:00 – 4:12Introduction to Evolutionary Psychology and Cultural Evolution
The hosts Dave Pietraszewski and David Pinsof introduce the podcast episode featuring guest co-host Christina Moya and guest Rob Boyd. They discuss the history of evolutionary psychology, the pioneering work of Rob Boyd and Pete Richardson on cultural evolution, and how these ideas fit within the broader Darwinian framework while celebrating scientific debate and respectful disagreement among researchers.
Rob Boyd and Pete Richardson pioneered the study of cultural evolution
“Rob Boyd and Pete Richardson uh pioneered the study of cultural evolution” 1:55
Dave and I are of the camp that it can be reconciled
“I think Dave and I are of the camp that uh it can be reconciled” 2:33
024:16 – 12:01Origins of Cultural Evolution and Evolutionary Theory in the 1970s
Rob Boyd joins the conversation to discuss how he and Pete Richardson began studying cultural evolution in the mid-1970s. They explore the landscape of evolutionary theory at the time, including sociobiology, game theory, the influence of figures like Richard Alexander and E.O. Wilson, and how population genetics methods provided tools to model cultural transmission alongside biological selection.
we Pete and I got started in the mid-1970s
“we Pete and I got started in the mid-1970s” 5:19
you needed those tools to do a proper job of asking what natural selection would do
“you needed those tools to do a proper job of asking what natural selection would do” 11:36
Dave Pietraszewski, David Pinsof, and Rob Boyd discuss how cultural information transmits differently than genetic traits, exploring developmental biology, phenotypic evolution, and the historical differences between UC Davis selectionist biology and other frameworks.
Farms can't spread the way the idea about how to farm can spread.
“farms can't spread the way the idea about how to farm can spread” 12:41
To understand how you got there from fins, you really do need to understand developmental rules.
“to understand how you got there from fins, you really do need to understand” 14:48
The speakers examine how rapid evolutionary changes occur across species like anoles and guppies by acting on standing genetic variation rather than waiting for new mutations, prompting broader reflections on evolutionary pacing and human behavioral sciences.
Morphology evolves fast because it involves many genes each with small effect.
“it evolves fast, not because it's one gene, it evolves fast because it's many genes, each with small effect.” 23:38
0524:06 – 30:05Evolutionary adaptations, human cognition, and fossil records
Rob Boyd and Dave Pietraszewski discuss evolutionary biology, the heritability of menopause, and debates surrounding human cognitive adaptations and fossil species classification. Boyd reflects on views of the human brain, comparing species-typical traits with variation across populations and referencing paleontological discoveries.
And her there were some problems with her work, but it's been done twice since, and estimates are about the same.
“it's been done twice since, and estimates are about the same.” 24:52
And now he's got pretty good evidence that it had a significantly different mode of locomotion
“significantly different mode of locomotion” 28:25
0630:06 – 36:07Modularity of the brain and animal instinct behaviors
Rob Boyd and David Pinsof discuss whether the brain contains specialized modules, contrasting evolutionary psychological approaches with neurobiological perspectives and instinctive animal behaviors like beaver dam building and bird nest construction.
And those little beavers seem to know how to do that without ever having seen a dam being built.
“without ever having seen a dam being built.” 32:26
And so that makes me skeptical of the neurobiological arguments.
“makes me skeptical of the neurobiological arguments.” 33:10
0736:07 – 39:20Recollections of John Maynard Smith and Academic Honesty
Dave Pietraszewski, David Pinsof, and guest Rob Boyd discuss the virtues of intellectual honesty in science and share personal memories of interacting with evolutionary biologist John Maynard Smith at conferences and lectures.
Rob Boyd recalls John Maynard Smith as an intellectual hero who was remarkably honest and actively engaged with students during lectures.
“John is my intellectual hero and um and uh he was an honest guy that way.” 37:25
Rob Boyd describes his daily breakfasts with John Maynard Smith during an academic school in Austria.
“So, you know, at 6 30 every morning, he and I were there at the beginning of the line to get breakfast.” 38:47
0839:20 – 48:11Disagreements on Cultural Evolution and Human Psychology
The hosts and Rob Boyd examine the core theoretical disagreements regarding cultural evolution, contrasting the view that humans possess a psychology shaped to acquire cultural practices without full adaptive understanding against traditional adaptationist models.
Rob Boyd argues that natural selection favored a human psychology prone to adopting behaviors from others even without an adaptive reason to understand them.
“selection has favored a psychology that does stuff that causes people to do stuff that they see people around them doing” 41:38
Dave Pietraszewski, David Pinsof, and guest Rob Boyd discuss the evolutionary explanations for extreme cultural behaviors like celibacy and group sacrifice, contrasting modular psychological accounts with cultural evolution and group-level selection of norms.
Selection cannot endow humans with drives like constant sexual activity regardless of context due to biological and social trade-offs.
“selection can't endow us with you know have sex no matter what, because” 49:28
The speakers debate the integration of evolutionary psychology with cultural evolution, examining how complex technological artifacts like kayaks, bicycles, and kinship structures develop over time through trial and error versus innate cognitive modules.
While complex artifacts like kayaks do not have dedicated innate cognitive modules, human cognition is capable of processing and adopting such tool-like innovations.
“There's no kayak module, but there's maybe is like, you know, a cock” 54:55
Rather than specific modules for complex modern inventions, human minds more plausibly possess broader intuitive physics or tool-use cognitive systems.
“more plausibly there are folk physics modules” 59:25
Dave Pietraszewski, David Pinsof, and guest Rob Boyd discuss the relationship between evolved psychological adaptations and cultural evolution, examining whether sophisticated cognitive mechanisms complement cultural processes and how to disentangle genetic versus cultural explanations for universal behaviors like reading and marriage.
cultural evolution and culturally adaptive processes at the same time
“cultural evolution and culturally adaptive processes at the same time.” 1:00:27
The idea that our brain is just a shapeless mass with no predispositions, that's just obviously stupid
“The idea that our brain is just uh you know a shapeless mass with no predispositions, that's just obviously stupid.” 1:05:08
The speakers discuss quantitative questions about human predispositions, credulity regarding social cues, and whether motivations or the cost-benefit calculations around conformity and social norms are shaped by cultural environments or innate propensities.
we're predisposed strongly to think what people around us do must be sensible
“because we're predisposed strongly to think what people around us do must be sensible” 1:06:21
we have an innately predisposed propensity to obey social norms
“we are innately predisposed, or innately, we have, you know, reliably developing whatever you want to call it, uh um propensity to obey social norms.” 1:11:52
Host Dave Pietraszewski and guest Rob Boyd discuss the evolutionary origins of morality and norms, debating whether moral outrage and rule-following stem from long-term evolutionary selection, social costs, or internalized cultural learning. Drawing on fieldwork in Fiji, they examine how deeply held moral beliefs and local norms shape human behavior and emotional responses across different timescales.
Rob Boyd suggests that our intrinsic motivation regarding moral violations is not merely a calculation of powerful people's costs and benefits, but something that evolves through models of social interaction.
“our sense that some things are right and some things are wrong there's morality” 1:13:13
Rob Boyd shares an anecdote from fieldwork in Fiji illustrating how strongly local cultural norms regarding women's clothing and behavior can temporarily override personal intuitions.
“I had this overwhelming that woman needs to put some clothes on” 1:18:13
The speakers—Dave Pietraszewski, David Pinsof, and Rob Boyd—examine multiple timescales operating in cultural evolution, distinguishing between genetically evolved intuitions, childhood norm internalization, and in-the-moment incentives. They conclude that many debates in behavioral science persist due to a lack of precise natural language distinctions and vocabulary.
David Pinsof outlines multiple timescales for social costs and conformity, ranging from intergenerational evolutionary adaptations to childhood socialization and immediate incentive structures.
“intergenerational evolutionary timescales that we're talking about” 1:19:42
Dave Pietraszewski and Rob Boyd reflect on how scientific progress and debates are often hindered by imprecise distinctions in everyday 21st-century English vocabulary.
“what typically is failing us is that there's just distinctions that are not made” 1:23:08
Guest Rob Boyd joins hosts Dave Pietraszewski and David Pinsof to discuss the adaptationist paradigm, contrasting rigid constraints with developmental pathways that shape biological variation. Rob Boyd references Lensky's long-term E. coli experiments to illustrate how rare neutral mutations and improbable events can overcome apparent limitations in evolutionary trajectories.
the adaptationist paradigm is uh it's not a paradigm, it's a heuristic.
“the adaptationist paradigm is uh it's not a paradigm, it's a heuristic.” 1:27:09
I think most of the things we ha we see in biology are things that shape the patterns of variation that selection can work on.
“most of the things we ha we see in biology are things that shape the patterns of variation that selection can work on” 1:29:27
The speakers examine whether rapid environmental changes and non-equilibrium conditions undermine adaptationist models. Rob Boyd explains that variation operates across multiple timescales, noting that organisms may respond to temporal averages or stationary distributions rather than reaching a static equilibrium.
there's variation on all kinds of timescales, right?
“there's variation on all kinds of timescales, right?” 1:35:05
it's not an imprinciple thing. It's just one of the things you have to take into account
“It's not an imprinciple thing. It's just one of the things you have to take into account” 1:35:58
Rob Boyd discusses with the hosts how the timescale and amplitude of environmental fluctuations during the Pleistocene prevented the emergence of agriculture and large-scale cooperation among non-relatives, contrasting those conditions with the stable Holocene period.
the timescale of fluctuations during the last glacial was too short
“the timescale of fluctuations during the last glacial was too short” 1:36:36
Pleistocene climate variation was so great that the social institutions necessary to support large-scale cooperation couldn't have evolved
“Pleistocene climate variation was so great that the social institutions necessary” 1:39:13
181:39:50 – 1:48:24Analytical Models versus Computer Simulations in Evolutionary Research
Rob Boyd and the hosts explore methodological approaches in cultural evolution, comparing analytical models with agent-based computer simulations, discussing issues of code reliability, replication challenges, and the tendency for mathematical and simulation work to become decoupled from empirical behavioral observations.
95% of modeling and reciprocity is responding to previous models of reciprocity and almost none of it is in response to questions about observed behavior
“95% of modeling and reciprocity is responding to previous models” 1:47:18
Dave Pietraszewski, David Pinsof, and guest Rob Boyd discuss the strengths and limitations of analytical models compared to agent-based simulations in evolutionary theory. They explore how mathematical equations provide deep conceptual intuitions, whereas simulations can sometimes obscure the underlying mechanisms unless researchers perform rigorous experimentation.
the key is to find simple enough representations of some problem that you can make analytical progress
“the key is to find simple enough representations of some problem that you can make analytical progress” 1:49:35
I have seen articles where they don't give a good intuition of why it resulted the work that they did
“I have seen articles where they don't give a good intuition of why it resulted the work that they did” 1:54:39
The speakers examine how evolutionary social science and biology differ from fields like economics and physics regarding training in mathematical theory. Rob Boyd highlights that unlike economists, biologists often lack deep training in formal modeling, which can lead to a disconnect between empirical work and theoretical foundations.
it's not a norm that practitioners understand the mathematical theory
“it's not a norm that practitioners understand the mathematical theory” 1:56:46
in economics, now economics has become very empirical
“in economics, now economics has become very empirical” 1:57:27
Host Dave Pietraszewski and guest Rob Boyd discuss the integration of theory and empirical work in the evolutionary sciences and psychology. Boyd reflects on how his views have evolved over the decades, expressing increased skepticism about cultural group selection and conformist transmission based on recent empirical findings and theoretical limitations.
I used to be more gung-ho about cultural group selection than I am now.
“I used to be more gung-ho about cultural group selection than I am now.” 2:03:24
And I'm less convinced about conformism than I used to be as a learning strategy.
“I'm less convinced about conformism than I used to be as a learning strategy.” 2:05:06
The hosts and Rob Boyd discuss the narrowing gap between cultural evolution and evolutionary psychology. After concluding the scientific discussion, the hosts wrap up the episode with informal banter regarding podcast merchandise, Patreon support, and minimalist t-shirt designs.
David Pinsof and Dave Pietraszewski thank guest Rob Boyd and discuss the relationship between cultural evolution and evolutionary psychology.
“you've been very gracious over the years” 2:08:41