If evolution is real, then all members of a species should evolve, just not a few.
The other thing to point out here is that individuals don't evolve.
Evolution is something that affects populations, not individuals.
And, has been pointed out, if a species gets split into two populations (by, for example, half the members moving into a new area, such as down from the trees and into the grass lands), both populations will evolve; just not necessarily in the same direction or at the same rate.
Does that answer your question, or are you still puzzled?
The Darwin theory is how old and before so much more technology and studies to prove otherwise? Monkeys umm nope that's not what I see when I look at me or my beautiful children. Nothing that reminds me of an ape