Tommy Can You Hear Me? Auditory Capabilities in Early Hominins

Language is beyond a doubt one of the cornerstone traits of humankind, and with the capability to speak comes the inexorable need to hear well. The sense of hearing originates of course from the external soft-tissue ear, but as well from the internal cranial structures at the temporal bones underlying ears. In a comparative anatomy study from Binghamton University in New York, researchers predict the auditory capabilities of individuals from the species Australopithecus africanus and Paranthropus robustus, with comparison to modern humans and chimpanzees. Analysing outer and middle ear bony structures, including preserved auditory ossicles from the South African hominins, the researchers determine that the two taxa are largely derived toward modern humans in their acoustic anatomy, but with more primitive incus and stapes resembling those of a chimpanzee. The study presents an interesting case study in the use of observable traits as proxies for interesting, more "intangible" properties of extinct organisms. To a cautious and limited extent, bone structure of the hominin inner ear allows prediction of power transmission for various frequencies of sound; with an understanding of the vibrational mechanics of different vocalisations, one can then make careful assumptions about the possible linguistic capabilities of these early hominins. The researchers in the study are careful not to take this to the level of science fiction, and so make respectable and exciting claims regarding the use of auditory capability to determine paleoenvironment, linguistic behavior and intraspecies variation thereof, and cladistic relationships. The closeness of Paranthropus and A. africanus acoustic cranial morphology to both modern humans and chimps implies some reliability of these as traits for systematic analysis; this could represent a new opportunity for improved understanding of ancient hominin phylogenies, as early fossils continue to enter our view of the dawn of humanity.

Fig. 1Measurements of the middle and outer ear (A to C) and ear ossicles (D). Quam et al Science Advances 2015