when we first talked

The evolution of our ability to speak is a story worth pausing to appreciate. It has taken several million years to reach this moment where I can tell you about how it took several million years for us to get here. While animals like whales, elephants, and crows communicate in sophisticated ways, our vocal abilities are unique and part of what makes us human.

Paleoanthropologists study the anatomy of our vocal tract, the morphology of our ears, and even the structure of a specific bone in our throats to piece together how and when our speech abilities arose. Speech itself doesn’t fossilize, but the fossil record of our ancestors provides crucial clues about the origins of our ability to talk.

This story might begin between 400 and 360 million years ago when the first ancient tetrapods transitioned from water to land and developed lungs and a movable tongue. Controlling these with precision is essential for creating the varied sounds of human speech. Alternatively, it might start between 8 and 6 million years ago when our lineage split from that of chimpanzees and bonobos. Despite their sophisticated communication, these primates can’t speak like us, and our earliest hominin relatives probably couldn’t either.

The first fossil evidence for hominin vocalization comes from a juvenile Australopithecus afarensis skeleton dated to 3.3 million years ago. This evidence includes a hyoid bone, a small, fragile, U-shaped bone in the neck that in humans supports the tongue muscles. In chimps and most other living apes, the hyoid also supports laryngeal air sacs, which may help in making vocalizations louder and longer but would make human speech harder to understand. The hyoid of Australopithecus afarensis resembled that of chimps, suggesting they had air sacs and likely couldn’t speak like us.

Hyoid bones are rare in the fossil record. The next oldest hyoids, found in the Sima de los Huesos site in Spain and dating to around 450,000 years ago, belonged to Homo heidelbergensis. These hyoids resemble ours more than those of Australopithecus afarensis, indicating the likely absence of air sacs, but this alone doesn’t prove they could speak like us.

Members of our species have unique vocal tract proportions, with the mouth and pharynx being roughly equal in length, enabling us to produce distinct vowel sounds like a, i, and u. These sounds are critical for clear communication. While Neanderthals and other hominins might have had similar vocal tract proportions, allowing them to make these vowel sounds, the evidence is still debated.

Neanderthals also show anatomical features supporting speech. Their hyoids and ear structures suggest they could make and hear human-like speech sounds. For instance, the hyoid from Kebara Cave in Israel, dating to around 60,000 years ago, matches the internal structure of human hyoids, indicating similar use of muscles and ligaments for speech.

The ear anatomy of early hominins like Australopithecus and Paranthropus suggests sensitivity to mid-range frequencies, while later hominins like Homo erectus and Neanderthals had hearing ranges more like ours, crucial for understanding consonants.

Overall, the anatomical changes in our ancestors point to the development of distinct vowel and consonant sounds, essential for speech. While we can't confirm if these extinct relatives had language as we define it, there's no anatomical reason they couldn’t produce and hear human-like speech sounds.

As the only remaining hominins, we have the task of piecing together the story of our ancestors' speech abilities and using our own to tell this evolutionary saga. For more on the similarities between Neanderthals and us, check out our episode, “When We Met Other Human Species.”

Thanks to this month’s Eontologists: Sean Dennis, Jake Hart, Annie & Eric Higgins, John Davison Ng, and Patrick Seifert! Become an Eonite at patreon.com/eons for fun perks, including joke submissions like this one from Matty Dahman: Why did the T. Rex need a nap? Because he was wiped out.