Merijn L M Salverda et al.
PLoS genetics, 7(3), e1001321-e1001321 (2011-03-17)
Whether evolution is erratic due to random historical details, or is repeatedly directed along similar paths by certain constraints, remains unclear. Epistasis (i.e. non-additive interaction between mutations that affect fitness) is a mechanism that can contribute to both scenarios. Epistasis