  Life emerged on the Earth within the first quintile of its habitable window,
but a technological civilization did not blossom until its last. Efforts to
infer the rate of abiogenesis, based on its early emergence, are frustrated by
the selection effect that if the evolution of intelligence is a slow process,
then life's early start may simply be a prerequisite to our existence, rather
than useful evidence for optimism. In this work, we interpret the chronology of
these two events in a Bayesian framework, extending upon previous work by
considering that the evolutionary timescale is itself an unknown that needs to
be jointly inferred, rather than fiducially set. We further adopt an objective
Bayesian approach, such that our results would be agreed upon even by those
using wildly different priors for the rates of abiogenesis and evolution -
common points of contention for this problem. It is then shown that the
earliest microfossil evidence for life indicates that the rate of abiogenesis
is at least 2.8 times more likely to be a typically rapid process, rather than
a slow one. This modest limiting Bayes factor rises to 8.7 if we accept the
more disputed evidence of C13 depleted zircon deposits (Bell et al. 2015). For
intelligence evolution, it is found that a rare-intelligence scenario is
slightly favored at 3:2 betting odds. Thus, if we re-ran Earth's clock, one
should statistically favor life to frequently re-emerge, but intelligence may
not be as inevitable.
