  Evolutionary game dynamics in finite populations is typically subject to
noise, inducing effects which are not present in deterministic systems,
including fixation and extinction. In the first part of this paper we
investigate the phenomenon of drift reversal in finite populations, taking into
account that drift is a local quantity in strategy space. Secondly, we study a
simple imitation dynamics, and show that it can lead to fixation at internal
mixed-strategy fixed points even in finite populations. Imitation in infinite
populations is adequately described by conventional replicator dynamics, and
these equations are known to have internal fixed points. Internal absorption in
finite populations on the other hand is a novel dynamic phenomenon. Due to an
outward drift in finite populations this type of dynamic arrest is not found in
other commonly studied microscopic dynamics, not even in those with the same
deterministic replicator limit as imitation.
