Evolution seems to be a rational explanation, but part of the story escapes me.
A change to a single element is plausible - eg: a leg bone lengthens to allow access to higher fruits, and reproduction favours those who have this variation.
A simple joint (knee, finger etc etc) is very different. To make it work requires a genetic variation to two bones, blood vessels, tendons, muscles, nerve pathways etc. If any one variation is missing the joint will not function. A single change has no purpose.
Therefore evolution is improbable - a number of complementary variations, occuring at the same time, producing something so functionally useful it is reproduced in future generations.
So I am left with the conclusion that evolution, whilst improbable, is actually feasible - perhaps we don't yet know fully how it happens. The alternative (for me) is the product of a fantasy to explain something real by reference to that for which there is no evidence, just faith.