# Forest Troop Study A natural experiment in cultural transmission, published by [[Robert Sapolsky]] and Lisa Share as **"A Pacific Culture among Wild Baboons: Its Emergence and Transmission"** in *PLOS Biology* (April 2004, volume 2, issue 4; DOI 10.1371/journal.pbio.0020106). The paper documents a savanna baboon troop in Kenya — Sapolsky's long-term field site, studied since 1978 — in which a tuberculosis outbreak selectively killed off the most aggressive males, after which the troop developed and *maintained for more than a decade* an atypically peaceful culture, transmitted to new males who migrated in. It is one of the most-cited empirical examples in animal-behavior research of **cultural transmission of social norms in a non-human primate population**. ## What happened The setup. Sapolsky and Share had been studying "the Forest Troop" — a wild savanna baboon (*Papio cynocephalus*) troop in the Maasai Mara — since the late 1970s, collecting behavioral data and physiological samples on individually-identified animals. The shock. Beginning in the mid-1980s, a neighboring troop (the "Garbage Dump Troop") had started raiding a tourist-lodge waste pit for food. Because baboon social structure is despotic — high-ranking males eat first and best — only the most aggressive males in the *Forest* troop muscled their way to the dump and acquired the high-fat scraps. The dump's meat was contaminated with bovine tuberculosis, and the baboons who ate it contracted the disease. By the time the outbreak resolved, **roughly half the adult males in the Forest Troop had died — and those were systematically the most aggressive ones**. The selection was unusually clean: only males who out-fought their way to the dump caught TB; the more subordinate and less aggressive males never got near it. The aftermath. The post-outbreak troop had a dramatically skewed sex ratio (many fewer adult males than usual) and was composed of males pre-selected for being on the less-aggressive end of the spectrum. Sapolsky and Share documented several behavioral changes: - **High rates of male-female grooming and affiliation** — atypical for the species - **A relaxed dominance hierarchy** — ranks were still present, but the brutality of enforcement was reduced - **Less harassment of low-ranking males** — and correspondingly **lower glucocorticoid levels** in those low-ranking males (see [[HPA Axis]]) - **Faster reconciliation** after the conflicts that did occur So far, this is not surprising. Remove the aggressive individuals and the remaining group is less aggressive. **The interesting finding is what happened next.** ## The cultural-transmission finding Savanna baboons follow a standard primate pattern: **males disperse**. Around adolescence, males leave their natal troop and migrate into a different troop, where they spend their adult lives. This means that **within a decade or so of the outbreak, no males remained in the Forest Troop who had been there during the die-off.** Every adult male was a migrant who had grown up elsewhere — under normal, aggressive baboon-troop conditions — and joined the Forest Troop sometime after the outbreak. And yet *the peaceful culture persisted*. The new males, who had been raised in normal aggressive troops, adopted the Forest Troop's relaxed norms after immigrating in. They were not the original peaceful cohort, and they had not been raised with these norms. They learned them on arrival. Sapolsky and Share documented that the transition took roughly six months — new males arrived behaving normally aggressively, were socially "trained" by the resident females and the existing low-aggression males (through selective grooming, selective affiliation, and the absence of normal dominance challenges from the resident males), and within months had shifted their behavioral repertoires to match. The conclusion, framed carefully in the paper: the unusual culture was being **transmitted across generations of individuals who had not experienced its origin**, supported by the resident females (who are the philopatric sex — they stay in the natal troop) and the existing male composition. ## Why it matters The finding is widely cited because it bears on three long-running debates. ### 1. Is "culture" a real phenomenon in non-human animals? Field biologists in the 20th century used "culture" cautiously for non-humans. The Forest Troop study is one of several cases (along with chimp tool-use traditions, killer-whale dialects, etc.) that built the contemporary consensus that yes, **non-human animals transmit learned behavioral norms across generations in ways that resemble human culture in structure if not in scale**. The peaceful Forest Troop is a particularly clean case because the origin event is documented, the personnel turnover is documented, and the norm persistence is documented across at least a decade. ### 2. Are violent hierarchies inevitable in tournament species? The standard sociobiological story for baboons is that male-male competition and aggressive hierarchies are evolved features of the species, with population-level near-inevitability. The Forest Troop is a counterexample: *within a tournament species, a population-level cultural shift toward lower aggression is possible, durable, and self-sustaining* once seeded. This does not erase the evolutionary substrate, but it complicates the "it's just biology" story. ### 3. Can social norms transmit across cohorts who didn't originate them? The classic worry about social-norm change is reversion: even if you change behavior in cohort A, won't cohort B revert to the underlying drive? The Forest Troop suggests that **resident-imposed norm pressure on incoming members can sustain a non-default equilibrium for years**, possibly indefinitely. The mechanism in the troop was the females and the existing males training newcomers; the analog in human institutions would be the persistent norm-pressure of established workplaces, communities, and political cultures on new entrants. ## RWKB applications The Forest Troop is rhetorically useful in the vault for two related arguments. ### Against "human nature" defeatism A staple of right-coded argument against any progressive social project is that the proposed change runs counter to deep human nature and will therefore fail. The Forest Troop is a vivid counter-example *in a species widely held up as a model of aggressive male competition*: a single die-off, a few years of new norms, and a culture is reset and sustained across generations. The argument is not "humans are baboons and can therefore be transformed" — it is that even in a species more aggressively hierarchical than humans, hierarchy and aggression are partly cultural and partly remakeable. ### Against "you can't change adult behavior" The new males who migrated into the Forest Troop were not children; they were adolescent and adult baboons fully socialized into normal aggressive troop dynamics. Within six months they had shifted. The analog for human institutional culture (workplaces, military units, communities) is that **culture change is possible at the level of new entrants encountering an established norm regime**, not only at the level of raising new generations from scratch. This bears on the empirical question of whether (e.g.) deradicalization programs or restorative-justice institutions can work; the answer here suggests that the cohort-pessimism case is overstated. ## Caveats and pushback - **Sample size.** It is one troop. Sapolsky and Share are explicit about this. The finding has not been replicated by re-running the experiment (an obvious ethical impossibility for primatologists). - **Selection bias in the die-off.** Some critics have argued that what persisted was not a *culture* but a downstream effect of the changed sex ratio and the prolonged absence of any particularly aggressive males. Sapolsky and Share's response is that the persistence beyond the original cohort's tenure is the key fact, and the changed sex ratio normalized within years while the culture persisted. - **Transferability to humans.** The case for cross-species inference cuts both ways. If one rejects Peterson's lobster inference, one should be cautious about generalizing baboon findings as well. The right reading is that the Forest Troop is a *demonstration* that cultural-norm change is biologically possible in a tournament species, not a *proof* about human politics. ## See also - [[Robert Sapolsky]] — the researcher - [[Dominance Hierarchies]] — the broader context - [[HPA Axis]] — the physiological measures used in the study - [[Behave]] — Sapolsky's book covers the Forest Troop story in detail - [[Psychology]] — subject hub