Male macaques who use stone tools show different social patterns than non-users

On Koram Island in Thailand, a population of long-tailed macaques lives with a peculiar divide running through it. Some members of the group use stones as tools—cracking open shellfish and nuts with deliberate strikes. Others do not. Researchers studying this hybrid population discovered something unexpected: the tool users and non-users were not simply different in what they ate or how efficiently they foraged. They were different in how they belonged to the group itself.

The question driving the study was straightforward but had gone largely unexamined in primate research. Scientists knew that tool use conferred nutritional advantages and that younger animals learned the behavior by watching older ones. What remained unclear was whether picking up a stone and using it as a tool changed how an animal moved through its social world. Did tool users occupy different positions in the hierarchy? Did they groom differently? Did they prefer the company of other tool users, the way humans might bond over shared practices?

To find out, researchers examined grooming patterns—the social glue that holds primate groups together. They watched which animals groomed which other animals, how often, and for how long. They mapped these interactions as networks, the same way epidemiologists track disease spread or sociologists study human friendships. The results revealed a striking asymmetry. Males were significantly more likely to use tools than females, a sex difference unrelated to dominance rank. A high-ranking female was no more likely to pick up a stone than a low-ranking one. Tool use appeared to be its own thing, separate from the traditional hierarchies that structure primate life.

But the real discovery lay in the grooming networks. Tool users and non-users maintained similar overall levels of social connection. They groomed at similar rates. They had similar numbers of grooming partners. On the surface, they were equally embedded in the social fabric. Yet when researchers looked more closely at the pattern of associations, a preference emerged among the non-tool users. They tended to groom with each other. They clustered together. The tool users, by contrast, showed no such bias. They groomed with both other tool users and non-users indiscriminately. They were, in a sense, more socially promiscuous.

This finding suggests something subtle about how technology integrates into animal societies. Tool use did not elevate an individual's status or create a privileged class. It did not isolate tool users into their own social sphere. Instead, it appeared to loosen the bonds of affiliation based on shared behavior. The non-tool users maintained stronger in-group ties, perhaps because they shared a common way of life. The tool users, having adopted a different foraging strategy, were less bound by that particular form of kinship. They moved more freely across social lines.

The implications ripple outward. In human societies, technology often becomes a marker of identity and a basis for social clustering—think of how shared digital practices now shape friendships and communities. This study of macaques suggests that the relationship between technology and social structure may be more complex and less deterministic than we assume. A behavior that changes how you feed yourself need not change how you relate to others. It can, paradoxically, make you less tribal, not more. As researchers continue to study populations where tool use and non-use coexist, they may uncover deeper patterns about how innovation spreads through groups and how groups themselves adapt when some members choose a different path.