First Words
by Alex Hawes
Although studies of animal behavior have revealed astonishing complexities in animal communication, including the capacity for aspects of language in certain species, we humans are the only species with a natural "spoken" language. While apes have been able to learn sign language and other forms of symbolic communication, they are physically incapable of reproducing human speech. The mouth, lips, and tongue are obviously important body parts in the formation of spoken words and are more mobile in humans than apes. We also are able to shape sounds more precisely, because our larynx, or voice box, and our epiglottis (the cartilage that prevents food from going down your windpipe) seem to be perfectly adapted for maximum control of air flow. These anatomical features are unique to humans, although parrots and other birds can mimic human speech with their own specialized vocal apparati. Consequently, attempts to teach apes to talk have failed.
But when did the evolution of language and speech occur within the hominid lineage? That question has provoked fierce debate among paleoanthropologists and anatomists alike. The soft tissue of the throat does not fossilize, so scientists have not been able to trace directly the evolution of the full range of anatomical traits allowing speech production. Beginning in the 1970s, certain researchers began looking at the bones of the skull, features that indeed can preserve well in the fossil record, in order to find clues to unravel this mystery.
The "flexion" of the base of the skull, the degree to which the floor of the skull is arched relative to the roof of the mouth, has been thought to have important consequences for the orientation of the voice box. The greater the degree of arch in the base of the skull, the lower the position of the larynx in the throat, and, as a result, the greater the ability to produce delicate speech (especially vowel sounds). In most mammals, the larynx, and the rest of the respiratory apparatus, is positioned quite high. While this orientation restricts the range of sounds one can produce, a highly positioned larynx does allow simultaneous swallowing and breathing. Our low larynx thus has its drawbacks (as you may have noticed the last time you tried to talk and eat at the same time). The rearrangement of the respiratory system must have had great adaptive value to outweigh the cost of this increased chance of choking while eating.
Phil Lieberman of Brown University and Jeffrey Laitman of Mount Sinai School of Medicine in New York argue that pre-humans, from the earliest australopithecines to our more recent Neanderthal cousins, did not have a larynx low enough to enable them to speak. Although Neanderthals may have been able to make certain verbal sounds, these "words" were probably very nasalized, which would have interfered with their clarity, and, as a result, their ability to be used in a precise and complex fashion. Only anatomically modern humans, which appear in the fossil record at about 100,000 years ago, seem to have had the necessary "basicranial flexion" (in paleoanthropological jargon) to allow speech, according to the theory's proponents.
However, within the last decade, scientists excavating an archaeological site in Israel, the Kebara Cave, have dug up and analyzed one tiny bone that, they believe, may single-handedly disprove the traditional theory that only modern humans could talk. The structure in question is the hyoid, a horseshoe-shaped bone resting freely in the throat, attached indirectly to the larynx, tongue, and base of the skull by ligaments and muscles. The hyoid is very fragile, and thus rarely found preserved as a fossil, even within relatively recent human remains. Despite decades of excavation at Kebara by researchers from Israel, France, and the United States, "It was a total fluke that this one was found in such excellent condition," according to Lyn Schepartz, a member of the excavation team and a professor of anthropology at the University of Cincinnati. This fossil, dated at 60,000 years old, represents the earliest complete hyoid in the fossil record anywhere in the world. The tiny hyoid may have huge implications for demonstrating the capacity for speech in fossil hominids. It is attached to the muscles controlling the tongue, and its delicate movement within the throat helps control the formulation of speech.
The Kebara hyoid once belonged to an otherwise anonymous Neanderthal individual who roamed coastal Israel during the Middle Paleolithic at the same time that anatomically modern humans were inhabiting parts of Africa. Schepartz and her Kebara Cave associates argue that this ancient hyoid falls within the range of variation of fully modern human hyoids, both in shape and size, as well as in the way the muscles attached to it. The Kebara hyoid differs markedly in appearance from those of modern great apes. Schepartz and her colleagues doubt the importance of the link between basicranial flexion and the capacity for speech. Their Neanderthal, they claim, could talk.
Schepartz faults the "linguicentrism" of researchers like Lieberman and Laitman who stick to their belief in modern humans' unique language abilities. However, Lieberman and Laitman are quick to respond to problems they perceive in the Kebara scientists' line of argument. First of all, they dismiss a theory based on a single fossil find. "You can't tell anything about Kebara," Lieberman asserts. However, without accepting such unique finds (including "Lucy," and other famous discoveries), we would not be very far in our understanding of human evolution.
More important, though, Lieberman and Laitman point to the importance of the position of the hyoid, and the rest of the vocal apparatus, rather than just its size and shape, as indicative of the capability to produce speech. An isolated hyoid, they assert, can tell us nothing about the orientation of the voice box. Infant humans have larynxes placed high in the throat; as a child develops, the larynx gradually descends, physically allowing a child to speak. The shape of the hyoid plays no role in the development of a child's ability to produce spoken words. The Kebara Neanderthal, suggest Lieberman and Laitman, may have had an infant-like laryngeal orientation, and could thus speak only as well as a human infant.
Paleoanthropologists have also looked beyond anatomical evidence in examining this contentious issue. "Language is part of an overall system that involves communication as well as cognition," reminds Schepartz. The cognitive abilities required for speech can also manifest themselves in other aspects of behavior. Some scientists have proposed that remains of statuaries, figurines, cave paintings, and ceremonial burial (though Neanderthals too buried their dead, but in a less ritualized fashion) from within the last 40,000 years indicate that anatomically modern humans alone had the understanding of symbolic expression necessary for spoken language.
Schepartz, however, looks as far back as 300,000 years ago for proof of the division of hominid home sites into areas for hearths, for refuse, and for tool-making, as well as (non-ritualized) burial to demonstrate abstract and complex thought. If we accept this reasoning, Neanderthals, and perhaps even their pre-cursor, Homo erectus, had the mental capacity for speech. Exactly which of these cultural practices corresponded with the actual emergence of speech in human evolution is, of course, anyone's guess. Moreover, the ape projects have shown us that, if taught, great apes too have the ability to use language in complex ways. Perhaps speech goes back even farther in the hominid line than we have imagined. If only fossils could talk....
(ZooGoer 24(6) 1995. Copyright 1995 Alex Hawes. All rights reserved.)
First Words (evolution of human speech)
Chipping Away (tool use)
Mindful of Thought (National Zoo's Think Tank)
