The origin of language. Krissia Liliana Dìaz Cornejo | Page 10

Teeth, lips, mouth, larynx & pharynx.
Human teeth are upright,
they are roughly even is
height  seem better adapted
for grinding and cheewing. 
they are also very helpful in
making sounds like p or b. 
Human lips have much more
intricate muscle interlacing
so their resulting
flexibility certainly helps
in making sound like p or b.