The findings of this study were published in the peer-reviewed academic journal Science Advances under the title "Vocal signals facilitate cooperative hunting in wild chimpanzees."
The study highlights the importance of vocal communication in evolutionary development, its link to group-level cooperation and that it may not be exclusive to just humans.
Team speak: Talking together for working together
Humans have evolved considerably from their distant ancestors in the animal kingdom, with certain evolutionary qualities having pushed us forward to where we are today.
This is important to note because, despite humanity's advances, there are several factors that would, at first glance, indicate a weakness over other animals.
For instance, humans lack fur to keep themselves warm, scales to protect them, claws or fangs to attack, and so on.
There are a few other qualities though, such as the ability to sweat and run long distances, a body structure geared towards throwing things, and a very high level of intelligence, that have put things in our favor.
But one of the most notable qualities that have helped push all of these things together is our ability to form groups and work together. This enabled humanity to thrive as hunter-gatherers all the way to forming agrarian societies and eventually civilizations.
Both of these factors saw humans continue to grow smarter, making use of their ability to use tools and innovate as well as communicate with one another. Over time, this saw the formation of sophisticated languages and collaborative efforts that increased in scale.
But are language and cooperation related? To a significant extent, yes.
Humans can cooperate together on small-scale and large-scale efforts, whether it be a simple hunting expedition or running a complex business. Both of these would be next to impossible without some measure of vocal communication.
In other words, if group cooperation is the backbone to humanity's success, then vocal communication is the backbone to group cooperation.
Now, is this exclusive to humans? No.
Despite humanity having far superior intelligence than other animals, there are other life forms on Earth with some degree of vocal communicative ability. In fact, it is far more widespread than many people would first assume.
The extent of this capability and its sophistication can vary on a case-by-case basis, ranging from simple mating calls, territorial marking and alarms to far more complex messages.
For example, prairie dogs are social animals and work together, using calls to sound the alarm when a predator is nearby. As many researchers have noted, their auditory calls to one another can be so specific that they can identify the type of predator, its size and its speed.
Further sophistication has also been seen in cetaceans like whales and dolphins, which are known to possess wide-ranging vocalization capabilities which are the subject of considerable scientific interest - especially considering the high level of intelligence cetaceans possess. In fact, some scientists believe that sperm whales might even have their own language.
But what is interesting is how these are used in connection to cooperation, and how they are essentially linked together.
In other words: Communication and cooperation coevolve.
But what about other primates? Do some of humanity's closest evolutionary relatives possess such a linked coevolution of cooperation and communication?
That was what this study sought to find out: Is the coevolution of communication and cooperation among primates present in other species, or is it something unique to humans and their ancestors?
Communication, cooperation in primates
It should be noted that many primates also possess a wide range of intelligence and do have noted, albeit limited, vocalization capabilities - some of which are used in social aspects. This, again, varies from species to species.
A significant amount of evidence exists indicating that primates in the wild have communication methods among each other, something that might be absent among the same species in captivity.
But a few factors are important here: How many individuals are involved in the cooperative effort and how often does it happen?
Studies have been done in the past on this subject, specifically among monkeys. However, this is less understood among great apes, which are humanity's closest relatives.
Chief among these relatives is the Pan genus, which consists of bonobos and chimpanzees who share around 99% of their DNA with humans. Much has been written about how closely related these species are to humans, with one 2003 study even having argued that chimpanzees should be included among hominids.
Chimpanzees are intelligent and adaptable, making their homes in a variety of different biomes. They have their own social structures and hierarchies and even engage in some proto-political alliances and groupings within themselves. Some have even supposedly been able to learn sign language.
Chimpanzees are also capable of a limited degree of tool use to the extent that they even use a proto-form of medicine, pose noted vocalization and are capable of group activity, with two groups infamously having gone to war in the 1970s in what has become known as the Gombe Chimpanzee War, the conflict having been documented by famed anthropologist and leading chimpanzee authority Jane Goodall.
But do chimpanzees have coevolved communication and cooperation as humans do?
To answer that, the scientists behind this study took a look at what they described as an "iconic example" of cooperation in a group of over two individuals: Hunting.
Specifically, the researchers took a look at over 300 chimpanzee group hunting efforts that have been recorded over the span of 23 years in Uganda.
A large number of these hunts tended to focus on tree-dwelling monkeys. This is important because these hunts are often spur-of-the-moment decisions for when a troop of these monkeys is detected.
The number of chimpanzees involved in each hunt can vary, but kills are more likely when more chimpanzees are involved in each hunt.
But in these dense forests, visibility is low. As such, vocal communication can be key.
These communications are done via "barks," with the bark used in hunting having been shown to be different from other barks in other contexts.
In other words, the bark here is specific to the context of hunting.
But how effective are they? Do they make cooperation more efficient?
According to the researchers, the answer is yes.
"Strikingly, following the production of hunting barks, we observed more hunters joining, greater speed in beginning the chase, and a shorter time to make the first capture."Zarin Machanda
"Strikingly, following the production of hunting barks, we observed more hunters joining, greater speed in beginning the chase, and a shorter time to make the first capture," explained study co-author Zarin Machanda of Tufts University.
It is unclear exactly how this works, and further study would be needed to better ascertain exactly why this happens.
But what seemingly is certain is that communication and cooperation are still closely linked together - to the point where it seems to be that it isn't specific to just humans, but also to our closest evolutionary ancestor, chimpanzees.