According to new research, bonobos -- our closest relatives in the animal kingdom -- might be able to give us an unprecedented peek at the evolution of human speech.
This particular species of great ape, scientists now say, uses sound to communicate in a way that's remarkably similar to a human infant. They may be the only other species which does so.
The study, published Tuesday in the journal PeerJ, focuses on bonobo "peeps". Those are high pitched squeaks that the animals use to communicate with one another. But here's the cool part: Those peeps may sound simple, but they're actually closer to human speech than anything else in the animal kingdom.
The researchers say these peeps are a lot like the sounds infants make before they learn to talk (which are called protophones). Baby babble is distinguishable from your standard animal grunting because it doesn't vary acoustically based on the emotional context of the babbling. A baby babble is a baby babble, which stands out in an animal kingdom full of sounds that only come out in particular contexts, like aggression, alarm, attraction or pain.
But bonobo babbling seems to work the same way. Under close examination of over 11 hours of recordings for each member of a bonobo community, researchers found that bonobos made these sounds in different contexts, requiring their fellow apes to read different meanings into acoustically identical vocalizations. The bonobos did have slightly different acoustic frequency for their very negative peeps -- ones related to distress and danger -- but used identical sounds for a wide range of neutral and positive circumstances.
That's a skill called structural flexibility, and they're the first non-human animals shown to have it.
This is generally considered an evolutionary precursor to speech as we know it, where a whole bunch of meaningless sounds are given meaning by social construct.
If so, we may have just pinpointed when our journey to unique speech in the animal kingdom really began: 6-10 million years ago, when our ancestry last converged with the great apes.
"More research needs to be done on our great ape relatives before we can make conclusions about human uniqueness," lead study author Zanna Clay of the University of Birmingham's School of Psychology said in a statement. "The more we look, the more continuity we find among animals and humans"