In the most basic utilitarian sense, our complex human languages evolved because they allowed us to convey information about the world from one individual to another. Language for early humans was incredibly important because it helped our ancestors tell each other when a predator was spotted nearby, when fruit was safe to eat, or if there was a dead water buffalo nearby that our ancestors could go scavenge some scraps from. This idea is the simplest idea for the evolution of human language, but it doesn’t truly convey everything we have come to do with our language over a couple million years of evolution.
Yuval Noah Harari expands on this idea in his book Sapiens, “a second theory agrees that our unique language evolved as a means of sharing information about the world. But the most important information that needed to be conveyed was about humans, not lions and bison.” What Harari means in this quote is that human language allowed our ancestors to gossip. This is an idea that Kevin Simler and Robin Hanson share in their book The Elephant in the Brain. They argue that language is often more about showing off and gossiping than it is about utilitarian matters such as conveying environmental information. They also argue that the use of language for gossip and signaling was one of the key drivers of the evolution of the human brain, rewarding our ancestors for being smarter and more deceptive, hence rewarding larger and more complex brains.
In Sapiens, Harari explains that many species of monkeys are able to convey basic information through specific calls that are recognized among a species, such as when a predator is nearby or when there is ample food nearby. Playbacks of sounds identified as warnings will make monkeys in captivity hide. However, studies haven’t been able to show that other species are able to communicate and gossip about each other in the ways that humans do from a very young age. Our use of language to convey more than basic information about our environment allowed humans to develop into social tribes, and it has sine allowed us to develop massive populations of billions of people all cooperating and living together.