Development of Speech and Hearing

Much less is known about the evolution of hearing than the evolution of vision.  There are some indications that sensing of sound such as the lateral line in fish occurred as early as 260 million years ago.  Reptiles sensed sound with jaw bones.  A transitional mammal “Yanoconodon allini” lived 125 million years ago and was known to have a middle ear.

The major evolutionary advance that separated humans from other animals was the communication established through speech and hearing.  Hearing, by itself, does not separate us from animals because higher animals have a good sense of hearing.  What truly separates us from the animals is our ability to have advanced communication using speech and hearing in tandem.  Although some animals do have a form of speech and hearing…. it is very crude by comparison.  For example, birds communicate with different types of chirps and chimpanzees and apes are known to communicate with crude forms of speech.  However, humans have taken speech to levels that are magnitudes beyond that of any other animal. It is safe to say that speech, as we commonly experience it, is unique to humans.

Many questions remain regarding speech development in humans.  Some experts suggest speech may have begun even 3-6 million years ago, but with a lengthy intermediate stage from ape language to human language.  The throat and ear bones of Neanderthals from 500,000 years ago indicate some ability for speech, although it certainly was not spoken as clearly as today.  de Boer has analyzed the evidence concerning speech development and concludes that modern adaptations for speech developed between 1.5 million and 500,000 years ago.  Late Homo erectus probably had some speech, and early Neanderthals and Homo sapiens likewise had speech.  The transition to the facial and neck traits needed for modern speech probably did not occur until only 40,000 years ago – at about the same time as significant human culture began.  John Hawkes, an anthropologist at the University of Wisconsin, has found eight hearing-related genes in humans that show signs of having systematically evolved over the past 40,000 years; some of the changes may have occurred as recently as during the past 2,000 – 3,000 years. 

Speech combined with hearing is a very recent evolutionary development and humans are unique in having developed it to advanced stages.