Scientists describe directional drift: evolution continues at the fitness peak

Researchers at Technion found that populations keep evolving even after reaching peak fitness, when selection pressure disappears. The effect, called directional drift, arises from the interaction between population variability and the curvature of the fitness landscape; the study was published in PNAS.

• Directional drift is a consistent push in one direction, not random change
• It stems from population variability interacting with landscape curvature
• Degeneracy: different trait sets can yield identical fitness
• Selection continues: beneficial mutations spread, harmful ones are phased out