Richard Prum on Birds, Beauty, and Finding Your Own Way
Richard Prum — evolutionary ornithologist at Yale and author of The Evolution of Beauty — joins Tyler Cowen for Ep. 126 to argue that bird beauty is not a proxy for genetic fitness but an autonomous aesthetic force, and that the best science comes from caring deeply about your particular subject rather than tracking what others deem important.
Key ideas
- Bird beauty arose, in part, because most birds lost the penis. In the lineage leading to most birds, the penis evolved away — Prum’s own theory is that females preferred mates without one, freeing themselves from sexual coercion. The result: females gained genuine freedom of mate choice, and what they chose was beauty. Sexual selection (the process by which mate preferences drive trait evolution) then ran autonomously, producing the extraordinary plumage and song diversity we see today.
- Aesthetic evolution is not the same as honest signalling. The dominant adaptationist view holds that bright colours and elaborate songs reliably advertise health and genetic quality — beauty as a résumé. Prum challenges this with the Fisherian runaway model: once a preference and a trait become genetically correlated, the whole system is self-reinforcing and can drift well beyond what any fitness signal would predict. The market analogy he uses is an ‘irrationally exuberant bubble.’
- Animal subjectivity belongs at the centre of the analysis. Bees make aesthetic choices about flowers (using colour, scent, and even static electric charge to judge how recently a bloom was visited); bird dialects diverge across regions for the same reasons human accents do — isolation, historical contingency, cultural transmission. Putting the animal’s subjective experience first, Prum argues, produces more accurate biology than modelling animals as optimisation machines.
- Birds have genuine culture, and have had it for tens of millions of years. Half the world’s birds learn their songs not from parents but from neighbours, decoupling genetic variation from the sounds they produce. Birds around Chicago, New York, and Boston sound different for exactly the same reason their human inhabitants do. That cultural transmission has been running far longer than anything humans have managed.
- The best science comes from caring about your subject, not from tracking the field. Prum describes a ‘minority style of mind’ in modern science: rather than asking what peers think is important, he asks what is the coolest thing he could do with his next day that would actually solve something. Situated knowledge — the view from a specific place and passion — opens opportunities that generalised, prestige-chasing work closes off.
Content
Why most birds are beautiful: the penis hypothesis
The puzzle of avian sexual dimorphism (why males of so many species are so much more elaborate than females) opens with an anatomical fact: unlike reptiles and most mammals, the vast majority of birds have no penis. In Prum’s telling, this was not a structural accident but the outcome of female preference. Once penis loss spread, females could no longer be forcibly fertilised. They gained what he calls ‘freedom of choice,’ and what they did with it — across millions of generations — was choose beauty, song, and elaborate display. Males who wanted to reproduce had to court rather than coerce, and had to invest in the nest once females made investment a condition of mating.
The correlated result is biparental care: eggs need warmth and protection until they hatch, chicks need feeding in the nest, and the growth period is so compressed (birds develop far faster than mammals of equivalent size) that two parents are almost always necessary. Whether biparental care caused female choosiness, or vice versa, Prum treats as genuinely open — the causality may run either way, or both.
The aesthetics argument: beauty for its own sake
Prum’s challenge to the standard adaptationist account (beauty = honest signal of quality) is central to his book and to this conversation. His target is the view that a peacock’s tail, or a bird of paradise’s dance, is really a health certificate — a costly display that only a genuinely fit individual can afford to produce. He does not deny that health and attractiveness are correlated. His point is that the correlation does not establish the mechanism.
The analogy he offers to Cowen: a violinist working flat out at a cadenza will break into a sweat. Do we admire the music because they are sweating, or do they have to sweat in order to produce the music we admire? The same observable data (extreme exertion, extreme display) is consistent with two entirely different causal stories. Prum argues that Fisherian runaway — named after the statistician R. A. Fisher, who first described it — provides the cleaner explanation for the diversity and arbitrariness of avian aesthetics. Once female preference and male trait become genetically linked, selection on one automatically selects on the other. The whole system accelerates, and there is no external anchor in mate quality to brake it.
Animal subjectivity: bees, flowers, and situated experience
A digression on pollination becomes one of the episode’s richest sections. Flowers are not communicating information — they are advertising a memorably rewarding experience, which is why most flowers are pollinated by generalist insects making aesthetic choices rather than hard-wired responses. Bees approaching a flower can detect its static electric charge (the hairs on their body stand up as they near), telling them how recently it was visited before they have even landed. This is a subjective experience that shapes choice. Prum uses it to argue that placing the animal’s inner life at the analytical centre, rather than modelling it away, is both more accurate and more scientifically productive.
The same principle applies to bird intelligence. Corvids (crows, ravens) and parrots are genuinely smart across multiple dimensions: a parrot has more pallial neurons — roughly, the neurons responsible for higher cognition — than a monkey with a brain four or five times as large. Ravens and crows may understand death, or at least recognise that a companion is physically present but no longer living. Birds know each other as individuals; albatrosses, which mate monogamously for decades, circumnavigate Antarctica in the intervening years and then return to find the same mate.
Bird culture and dialect
The claim that birds have culture is not metaphorical. Half the world’s birds are vocal learners — they acquire their songs from other members of their species, almost never from their parents. The decoupling of genetic variation from acoustic output is what makes bird song cultural: the same bird with the same genes would sound different had it been raised in a different neighbourhood. Populations diverge for reasons of isolation and drift, not because of ecology or genetics, producing dialects as recognisably local as those of the humans in the same city. Birds have been doing this for tens of millions of years, long before any human cultural tradition.
Ornithology, game theory, and the problem of multiple equilibria
Cowen asks whether ornithology suffers from the same proliferation of untestable models that economics does — many equilibria, many possible predictions, no way to adjudicate. Prum agrees it does, but treats this as a feature rather than a bug: nature is diverse, and a theory that generates multiple equilibria is not failing to predict so much as acknowledging that history matters. A large fraction of what we observe in birds — cooperative breeding in Australia, duetting distributions, which lineages have which traits — is historical persistence and path dependence rather than current optimisation. He estimates the history component at 30–50% for phenomena like duetting.
He also pushes back on the economist’s assumption that communication is about efficient information transfer. Much of what birds (and people) do in communication is suasion — persuasion and seduction — which is not the same thing, and which signalling theory handles poorly.
Technology and birding
Apps built by Cornell’s Lab of Ornithology — eBird for checklists, Merlin for AI-powered photo identification — have transformed amateur birding. Data uploaded in real time feeds citizen science and reshapes what professional ornithologists know about distribution and abundance. GPS transmitters and satellite tags are giving researchers complete life-histories of individual wild animals for the first time; transcriptomics (sequencing all the RNA a tissue is expressing at a moment) is opening questions about development and physiology that genomics alone could not answer.
Prum is warmly enthusiastic about all of it while admitting he remains old-school: he does not keep his checklist digitally in the field, which means his own data are less useful than a younger birder’s would be.
Finding your own way: the production function
The final segment is an intellectual autobiography compressed into a few exchanges. Prum grew up in rural Vermont, started birding at ten, and was for years the only young person he knew doing it — which meant he had to trust his own sense of what was worth pursuing. The habit stuck. He describes most scientists as looking sideways to calibrate what they should care about; he looks at the birds. His favourite Onion headline — ‘NSF studies show science is hard’ — frames his point: if science is hard and you are going to spend a lot of energy, the calibrating question should be what you find coolest to solve, not what the field currently deems important.
He cites Donna Haraway’s concept of situated knowledge: good science is not the view from nowhere but the view from somewhere specific, and caring about the particular instance — house wrens in Ohio, the hoatzin in the Amazon, Steller’s eider in the Arctic — is what generates the pressure to understand it deeply enough to produce real results.
Related
- Richard Prum — guest; evolutionary ornithologist; author of The Evolution of Beauty
- Tyler Cowen — host
- Evolution — concept; Fisherian runaway and sexual selection as evolutionary mechanisms