The weight of opinion seems to be turning against Gould's view of the level
of uncertainty in evolution. Many of the weird Cambrian creatures are now
being fitted into existing phyla and evolutionary paths, and many of the
Precambrian taxa have at least suggested affinities, though the possibility
of really strange creatures then retains greater support.
There is probably more support for the role of catastrophes in introducing
unpredictability. Any evolutionist (i.e., someone who accepts a large role
for evolution in the creation of living organisms) agrees that there is no
way organisms could have prepared for an asteroid impact or similar events,
so the effects are not easily predictable. On the one hand, some people
seem to give catastrophes and extreme role (Raup had a general-audience
book along these lines), whereas others see them as merely hastening the
replacement of less competitive forms with more successful ones.
If "guided" simply refers to God's control (regardless of His method), I do
not believe anything is unguided. Whether God, if He were to do it over
again, would make the same pattern of evolution is very moot. Creativity
would tend to argue for differences, but I cannot immediately think of any
stronger evidence bearing on the question.
Another factor that may make the course of evolution humanly hard to
predict is God's inclination to pick humanly unpromising beginnings for His
purposes. If He likes to pick the smallest nation, family, etc., why not
the least interesting-looking worm?