When We First Talked

Typically, I would start an episode of Eons by telling you about the discovery of some strange fossil or setting the stage for a world-changing event, like an ice age or an extinction. But today I want to try something a little different. Instead of thinking about a story, I want you to stop and think about what I'm doing here, literally, that I'm standing here and telling you a story. Because the evolution of our ability to speak is its own epic saga, and it's worth stopping to appreciate that. It has taken several million years to get to this moment where I can tell you how it took us several million years to get here.

And yes, there are other animals alive today that communicate in sophisticated ways, such as whales, elephants, and crows, to name a few. Still, our vocal abilities as a species are quite unique. They are part of what makes us human. From the anatomy of a particular bone in our throat and the proportions of our vocal tract to the morphology of our ears, paleoanthropologists are piecing together the puzzle of

when

and how this adaptation arose. And although speech itself does not fossilize, the fossil record of our ancestors and relatives can still give us important clues about the time

when

we

first

spoke.

Now, this story could begin between 400 and 360 million years ago, when the

first

ancient tetrapods transitioned from life in water to life on land and developed lungs and a mobile tongue. Controlling both precisely is important to creating the different sounds that make up human speech. Or it could begin about 8 or 6 million years ago, when our lineage (hominids) diverged from the ancestors of our closest living relatives, chimpanzees and bonobos. While there is no doubt that they can communicate with vocalizations, gestures, and expressions, they cannot speak like we do, despite decades of efforts to teach them how to do so.

And our first hominid relatives probably couldn't talk like we do, either. Because! The first fossil evidence that can be used to reconstruct hominid vocalization comes from the skeleton of a juvenile Australopithecus afarensis dating back to 3.3 million years ago. This special bone is called the hyoid. It is a U-shaped bone that is located in the neck just below the level of the jaw and does not connect to any other bones. Instead, it is held in place by muscles and ligaments. In humans, the hyoid is an important attachment point for the muscles of the tongue. The same thing also happens in chimpanzees.

But in chimpanzees (and most other living apes) it also helps support structures called laryngeal air sacs. Now, we don't know exactly what these things do. Some research has suggested that they might help make vocalizations louder and help primates call longer or more frequently without hyperventilating. But they also seem to introduce new, lower resonances into vocalizations and reduce differences between higher-pitched sounds. Both of these things would make human speech sound harder to understand. And here's the thing: the hyoid of Australopithecus afarensis looked more like that of chimpanzees and gorillas than ours. Which means this hominid probably had air sacs attached to its hyoid.

So their species probably couldn't talk like us. And that hyoid is the only one we have of any species of australopithecine. The hyoid is a small, fragile bone, making it one of the least known bones in the hominin fossil record. In fact, the next oldest hyoids we've found come from a site that is almost three million years younger. In that period of time, the Australopithecines disappeared and our own genus, Homo, evolved, and some populations even left Africa for Asia and Europe. And a cave in northern Spain called Sima de los Huesos is where the next oldest hyoids were found.

They are attributed to being about 450,000 years old and belonged to members of the species Homo heidelbergensis. This species may be the common ancestor of Neanderthals and our own species, Homo sapiens, or it could simply be a close relative of both. And although both hyoids at this site are incomplete, what is preserved looks much more like our hyoid than the hyoid of Australopithecus afarensis or a chimpanzee. So these hominids probably didn't have laryngeal air sacs. But that doesn't necessarily mean they could talk like us, at least not based solely on their hyoid bones. In addition to the lack of laryngeal air sacs, members of our species also have unique proportions of the vocal tract.

You can divide the vocal tract above the larynx, or larynx, into two basic parts. The mouth constitutes the horizontal part and the pharynx constitutes the vertical part: the piece between the mouth and the larynx. In adult humans, these two parts are approximately the same length. This allows us to form three of the different vowel sounds (a, i and u) and make them sound really different from each other. And almost all human languages ​​have at least three vowels, and they tend to be those three. This could be because they sound more different from each other, so they are less likely to be misheard.

But some anthropologists do not believe that other hominids had these same proportions. For example, researchers previously suggested that Neanderthals had much shorter vertical parts of their vocal tracts and longer horizontal parts. Human babies and chimpanzees also have short vertical segments of their vocal tracts and, as a result, cannot make those distinct vowel sounds. But that fossil site in Spain can also give us clues about this piece of the puzzle. Because there is an individual with an almost complete skull and all seven neck vertebrae that researchers have used to estimate the lengths of the two parts of the upper vocal tract.

They discovered that the horizontal part was actually only a little shorter than the vertical part. This makes the fossil's proportions more like those of a 10-year-old human child than an adult. And 10-year-olds can still make those same distinct vowel sounds, meaning this nearly half-a-million-year-old hominid probably would have been able to do it, too. Some of our more recent relatives also appear to have had vocal tract proportions similar to that individual. When anthropologists reconstructed the length of the vocal tract of an adult Neanderthal from France dating back to between 50,000 and 70,000 years ago, they found that the horizontal section of their upper vocal tract was slightly shorter than the vertical section.

Therefore, he could also probably make the full range of sounds found in human speech. And there is more anatomical evidence of speech in Neanderthals than just a reconstructed vocal tract. Returning to the hyoid bone, we have found two of these extinct relatives of ours. One of them comes from another cave in Spain and dates back to about 43,000 years ago. It is incomplete, but was described as "almost indistinguishable" from a modern human hyoid. The second is a little older, dating back about 60,000 years and comes from a site in Israel called Kebara Cave. It also looks a lot like our hyoid bones.

The scientists working on this bone even scanned it with CT scans to see if its internal structure matched that of a human hyoid. You see, bone can change or remodel its microscopic architecture over time, depending on how it is used. So if a Neanderthal used the muscles and ligaments that attach to their hyoid the same way we do, CT scans of our hyoids should look similar too. And they did it! Which means that both the exterior and interior of this Neanderthal's hyoid suggest that it was capable of making human-like speech sounds. But! Being able to make human-like speech sounds is only half the story; the other half is being able to hear them.

While paleoanthropologists have not found many fossil hyoids, they have found many skulls. These allow them to study things like the size and shape of the ear canals (and sometimes even the small bones of the ear) because they are contained within the temporal bones of the skull. And by comparing the fossils to the anatomy of living primates and humans, they can model the hearing ranges of our extinct relatives. Early hominids, such as Australopithecus africanus and Paranthropus robustus, have some features of their ears that are more like ours than those of a chimpanzee. For example, they have a slightly shorter and wider passageway that runs from the outside of the skull to the eardrum membrane.

And they have a hammer, one of the middle ear bones, that looks human. But the other two bones of the middle ear, the incus and stapes, are closer in size and shape to those of chimpanzees. And when their hearing abilities are modeled, they don't look like ours or a chimpanzee's. These early hominids appear to have been more sensitive to mid frequencies than modern humans or chimpanzees. The most human-like ear anatomy and hearing abilities appear to originate in our genus, Homo. Homo erectus fossils from Asia have some human characteristics, and Sima de los Huesos hominids and Neanderthals are even more similar in ear anatomy to Homo sapiens.

The same model of hearing used for early hominids predicts that later members of our genus probably had hearing abilities like ours. They lost some of the mid-frequency sensitivity seen in early hominids, but expanded their range of maximum sensitivity to include higher frequencies. It has been suggested that greater sensitivity to those higher frequencies is important for hearing consonants, especially t, k, f, and s. And the use of consonants is a key feature that distinguishes human language from most animal communications. These changes in ear anatomy and hearing ability go hand in hand with changes in the hyoid bone over time: early hominids were more similar to our closest living relatives, and members of our genus Homo are more similar. us.

And when we get to the Sima de los Huesos hominids and the Neanderthals, it seems like we have all the anatomy in place for different vowel and consonant sounds, which is pretty incredible! Now, we don't know if this means that these extinct relatives had language. This is still a big topic of debate and we don't have enough evidence to say either way. It could simply come down to how we define language. But what we can say is that there is no anatomical reason why they couldn't make and hear human-like speech sounds. And we know that Neanderthals were capable of very human behavior, such as caring for injured members of their groups and using objects as personal ornamentation.

So maybe they were storytellers too. As we are the only hominids left, it is up to us to piece together the puzzle of our ancestors' speech capabilities and use our own to tell this evolutionary story. Hey, if you want to learn more about all the ways Neanderthals were similar to us... as well as what happened to them, be sure to check out our episode, "When We Met Other Human Species." Now I have to say that this month's eontologists are: Sean Dennis, Jake Hart, Annie and Eric Higgins, John Davison Ng and Patrick Seifert. By becoming an Eonite at patreon.com/eons you'll get some fun perks, including submitting a joke for us to read like this one... from my friend Matty Dahman.

Why did the T Rex need a nap? Because he was annihilated. I need a nap after this script! Thanks Matty for submitting your joke. And as always, thank you for joining me in the Konstantin Haase study. Subscribe at youtube.com/eons for more deep time adventures.