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Searching for signs of when our ancestors’ sounds became speech

If your parent were paying enough attention, they may have carefully noted when you spoke your first words. Even your first gurgling vocalizations at just a few weeks old may have been recorded on camera or in a baby book, because it’s a very exciting thing when people start on the path to communicating through words. Unfortunately, this early milestone largely remains a mystery for humanity as a whole, because as amazing as it was to start communicating through symbolic sounds, humans were still ages away from being able to document this accomplishment. Scientist have been working for decades to find some forms of proof of when humans, or more likely, our primate ancestors, started talking to each other.

Modeling backwards from modernity

Since speech had to have come before written languages, anthropologists have had to look for indirect evidence of more sophisticated vocalizations in our ancestors. Stone Age tool complexity has been offered as a metric, with studies trying to compare the brain activity required in modern humans to what’s needed to recall certain words. However, between the use of modern human brains and relatively low-resolution brain imaging techniques, this hasn’t really been considered conclusive. Another concept has been to try figure out the growth of known languages’ phonemes, and then use that to backdate when they would have started from. The two models have wildly different dates though, ranging from 1.75 million years ago in the former, to just 100,000 years in the latter.

Examining ancient ears

Looking further back, some lines of research have focused more on the biomechanical influences on when speech as we know it would have even been possible. Going back around two million years, scientists have found some differences in primate ears that make for closer matches to what we have now. While modern chimpanzees, as our closest living relative, have hearing more tuned to low frequency sounds, a few fossils have evidence of when hominins started listening for higher frequency sounds. These higher pitches would have been very well suited to vocalizing in open spaces with “K,” “T,” “Th,” “F” and “S” phonemes, versus the lower pitches that travel better through dense foliage of forests. It doesn’t prove speech of course, but it does show how our ancestors were starting to move in that direction.

Some of these specializations definitely took place far enough back in time to be spread throughout the hominin family tree though, as Neanderthal ears have been found to be very similar to those in modern humans. The tiny and thus rarely found ossicular bones from the inner ear have recently been mapped in fossilized skulls using x-ray tomography. The bones are a close enough match for our ears that there would have been nothing in Neanderthal hearing to have kept these extinct relatives from utilizing sound as well as we can for communication.

Wired for words

Hearing symbolic vocalizations is one thing, but it’s obviously of little use if you can’t produce and understand those sounds as well. Fossils are going to have a very hard time ever providing evidence of the sophisticated lips, tongues and larynx that a human uses to shape specific sounds when we speak. One bit of soft tissue that can provide a clue though is our DNA. A gene called FOXP2 was first studied in relation to speech disorders, and further study has suggested that it is critical to our complex vocalizations. It appears to have mutated around 200,000 years ago from what you still find in modern chimps, and is thought to have been part of the Neanderthal genome as well. Among other functions, this gene is thought to have allowed for better control of facial muscles, helping our ancestors get more specific with their pronunciation than ever before.

Source: Origin of speech, Wikipedia

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