Fig. 1. evolutionary systems biology.

Systems biology examines how complex molecular networks mediate genotype–phenotype relationships within an organism. Phenotypes feed back on genotypes through their effect on fitness, which influences the probability that genotypes are propagated across generations. Evolutionary systems biology is concerned with the joint evolution of genotypes, networks and phenotypes. An evolutionary systems-biology approach would shed light on the cross-species translation problem by considering that molecular networks in two extant species derive from a common ancestor but have diverged due in part to exposure to different environments and selective pressures.