If a branch looks unlikely to yield the result, it's
lopped off rather than searched.
No way! There is no looking ahead.
I don't think I made the point clear.
One thing: There is not particular direction or "desired" outcome.
Once some variation arises and is selected for it may mean that other possible branches in evolutionary space are less easy to reach or impossible. Therefore the continued process isn't having to search every possible outcome. There are a smaller number of total steps to get from where it was to where it is.
But it isn't searching for a particular way out. It is a little like water flowing downhill. It doesn't have any preferences for which way but will find one way.
Water flowing once it has branched right at some point can't move back up hill and "explore" the left branch. Well, in general. It could back up and make a deep pool and flow the other way under some circumstances.
I think the above might be a slightly useful analogy.