"Intelligent life on a planet comes of age

when it first works out the reason for its own existence."

Comes of age ?
Reason for existence ?

I would have thought, Professor Dawkins*,
that a definition of intelligent life
would have nothing to do with a reason for existence
(which is just another form of Prime Mover, or god),
and indeed, truly intelligent life
would be way beyond the adolescent fantasy 
of seeking a reason for existence.

*in The Selfish Gene, 1976.