The troop, studied long-term near the Maasai Mara, had males who monopolised access to a tourist lodge rubbish site. Those males contracted bovine tuberculosis from contaminated meat and died, removing roughly half the adult males and disproportionately the most aggressive ones.
What followed was documented over the next two decades. Rates of male aggression towards females and low-ranking males stayed low, grooming rates rose, and physiological stress markers in subordinate animals were lower than in comparison troops. Crucially, the pattern persisted after the surviving males had died or left, and males transferring in from ordinary troops adopted the local style within months.
The result is genuinely striking, and its limits should be stated. It is a single troop, the change was accidental rather than designed, and there is no control troop with an equivalent history. It is best read as a well-documented natural experiment, not a general law about baboons.