If duplicated genes are retained then they
may either partially lose their ancestral function, thus, both are
required to maintain full functional activity, a process known as
sub-functionalisation, or neo-functionalisation may emerge where
one gene retains the original function and the other alters to
acquire a new function. A further model to explain retention of
genes via sub-functionalisation termed escape from adaptive conflict
(DesMarias and Ruahser, 2008) sees adaptive evolution driving
changes in the two genes