Expanding Beyond Great Apes

To date, research on gestural communication has been largely focused on great apes due to their close phylogenetic proximity to humans. However, including a broader range of species is essential for identifying evolutionary patterns. This international project involved six months of intensive fieldwork at the Punta Laguna protected area in Mexico, where researchers analyzed the behavior of 54 wild spider monkeys.

The study recorded over 700 gestures, discovering that these primates frequently combine signals into sequences of 2 to 4 gestures. "Our findings show that communication in spider monkeys is far more flexible and intentional than previously thought," explains Miquel Llorente, co-author of the study and researcher at the University of Girona.

"This research is a significant step forward for our group. It proves that the ability to sequence gestures—a fundamental building block of complex communication—isn't exclusive to great apes. By studying spider monkeys in their natural habitat, we are uncovering the ancient evolutionary roots of the social complexity that eventually led to human language." — Miquel Llorente.

High-Arousal Contexts and the "Redundancy" Strategy

The core of the research focused on the structure of gestural sequences. By analyzing 709 gestures recorded via focal video sampling, the team discovered that spider monkeys rely heavily on "redundant" sequences—repeating the same gesture or using different gestures with the same meaning—to ensure their message is received during intense social moments.

The study found that these sequences are predominantly used in high-arousal contexts, such as social play, agonistic encounters (aggression), and sexual interactions. Interestingly, while in many other primate species young individuals use more sequences as they "learn" to communicate, spider monkeys showed no significant differences across age groups or sexes. This suggests that sequencing is a robust, species-wide strategy used to manage social tension and ensure clarity when emotions run high.

"What makes this study unique is the setting and the species. By observing these monkeys in the wild at Punta Laguna, we've seen how ecological and social pressures drive the need for more complex signaling," says Miquel Llorente. "Our work at the University of Girona aims to map these communicative building blocks across the primate tree. Finding such structured sequences in a New World monkey species like Ateles geoffroyi allows us to push back the timeline of when these cognitive abilities first appeared in our ancestors."

Scientific Impact and Future Directions

By documenting these sophisticated behaviors, the Comparative Minds group reinforces its position at the forefront of primatology. This research not only bridges the gap between the communication of monkeys and great apes but also sets a new standard for studying gestural complexity in the wild. The findings suggest that the drive to combine signals—a precursor to the syntactic structure of human language—is a deeply embedded trait in the primate lineage, triggered by the complexities of social life.

Reference: Corral, E., Cardoso Rodriguez, S., Liebal, K., Llorente, M., & Amici, F. (2026). Gestural Sequences in Wild Spider Monkeys (Ateles geoffroyi). American Journal of Primatology, 88:e70156. https://doi.org/10.1002/ajp.70156