Only humans have the ability to communicate about the past? What
about bees? A bee can tell other bees where the flowers with the good
pollen are. There is a theory that song is older than language.
Language probably evolved very very gradually. Even today, some
languages have "song" like features, such as the tones in Chinese and
the clicks in Xhosa.
I think baby talk is a good model what early language was like. The
development of the brain shows a very gradual development. Even homo
erectus already had lateralization of the brain. There is no fundamental
difference between a human brain and an animal brain.
And don't forget that people who have had strokes in Broca's Area
of the brain can still think. It is a myth that language is necessary
for intelligence. Einstein was a genius but he had dyslexia and flunked
math. Some severely retarded people have normal language abilities and
some intelligent people have severe language disabilities. Math is also
a language.
The great scientist Maxwell first thought of concepts like
electromagnetism in the abstract. Only then did he think of equations
and words to express the ideas. The ideas came first; then the language
to express them.
http://www.delphi.com/paleolinguistic
http://www.delphi.com/paleoneurology1