There is many mathematical (using rather simplistic factors) models.
But the biggest unknown is the likelyhood to evolve
from a high animal to a concious smart intelligence.

There was like 150million years time on earth with high
animals, but only some the primates in recent time
got over the level of sniffing on others butts.

To evolve a concious intelligence is
not an automatism as many think of it.
its not even economical for most lifeforms, who
rather spend they energy on beeing faster, smelling better or breeding more.
(The local maximum in the evolitionary search)

I see the human intelligence more of a lucky coincidence
than an evolitionry automatism.