The ability to issue warnings is a common feature in animal communication. Alarm calls can warn group members about the presence of a predator, and can even provide information about the type of predator, as well as its location. Such warnings happen in real time, while the danger is present.

Humans do this too, of course, through screams (which are useful for raising alarm, but not really all that informative) and through language. Importantly, human language also has a unique feature called displaced reference, which is the ability to share information about a past or future event, or about something that is not present at the moment.

Displaced reference is found throughout all human languages and is, in fact, considered a primary hallmark of language. However, beyond humans and, curiously, a handful of insects like the honeybee (which is known for using distinct movements to provide spatial information about  resource location), displaced reference is rare in the animal kingdom. Among primates, humans are alone in possessing this particular communication skill. Or at least that’s what we thought.

Now, researchers at the University of St Andrews in Scotland have discovered that orangutans can use displaced reference to ‘talk’ about past events.

Adriano Lameira, a primatologist at St Andrews, carried out an intriguing study in the Ketambe jungle in Sumatra. He designed an experiment wherein a scientist draped in a sheet with one of four designs — tiger print, white, white with multicolored spots, and an abstract color pattern — would slowly crawl across the forest floor in proximity of an orangutan mother sitting in a tree. Once seen by the orangutan, this artificial ‘predator’ would pause for 2 minutes and then move along, out of sight.

There were 24 trials in all, and in 12 of these, the mother waited an average of 7 minutes before vocalizing an alarm call.  In one case, an orangutan waited nearly 20 minutes after she first spotted the ‘predator’ before raising a prolonged alarm.

This delay was not only observed when the orangutan was alone (i.e. when they perceived danger for themselves) but it was also observed when mother orangutans sensed their child was in danger (i.e. when they perceived danger for another individual).

So why did those orangutans wait before raising the alarm?

Lamiera proposes that the decision to call or not call may be linked to a perceived danger for others coupled with the need to not make matters worse. Vocalizing in the presence of a predator comes with a risk, as it could reveal the location of the orangutan and her infant, putting the latter in particular danger. Thus, the delay could be a safety-first maneuver, followed by the need to alert others and, importantly, teach the child about the danger that has just passed. Indeed, it seems that mothers with younger, less experienced offspring were more likely to emit a delayed alarm call than mothers with older offspring.

This is capacity for displaced reference has not been observed in other primates such as lemurs, monkeys, and great apes, which are known to raise vocal alarms as soon as an artificial predator is spotted.

As Lamiera and his colleague Josep Call explain in their paper published in Science Advances, these new findings point to a form of high-order cognition in orangutans.

“Postponing behavior in time and space inherently expresses a role of high cognitive processing of the stimulus and general intelligence,” they say.

“Our observations, thus, suggest a scenario for language evolution in hominids.”

In other words, displaced reference may be more than just a hallmark of language, it could be a fundamental component in its evolutionary development.