Breath Holding and Pre-Adaptation for Speech      One important adaptation that must have occurred in order for humans to speak is the ability to consciously hold one's breath. Other primates don't speak because they are physiologically unable to voluntarily hold their breath. Also, the range of sounds that humans can make is a result of our "descended" larynx. In humans the larynx is in a descended position. The only other known animals with this feature are the dugong, sea lion and walrus (Morgan 1997). In the case of humans, the larynx moves deeper into the throat, and no longer makes contact with the uvula, as in other apes.

Gorilla; Human

The larynx begins its descent after birth, between 4 - 6 months of age and by 18 months the larynx is in its final position at the base of the throat. This morphological character allows humans to take air in not only through the nose, but also through the mouth. This attribute also allows for choking and the risk of death by drowning in one's own fluids (Morgan 1997). What advantage would mouth breathing give us? Mouth breathing allows for increased intake of oxygen, allowing for greater endurance while running, for example. Mouth breathing also allows for more air to be taken into the lungs before a dive, very quickly (Morgan 1997). Certainly, if we consider our ancestors as purely savanna/dryland dwellers, then finding a good reason for this often dangerous adaptation is very difficult.