 As early hominin species began walking upright and the front limbs were no longer used for locomotion, the muscles in the chest no longer had to synchronize breathing with locomotion. The larynx moved to a lower position in the throat, and the pharynx developed, allowing early humans to modulate their breathing and vocalize in complex ways (Harris 1989, 77). Eventually they would speak, but before that they came to laugh in our human way: “ha ha ha” on the out-breath instead of “ahh ahh ahh” on the in-breath.