Before revision:  We analyze the "fossils" of the evolutionary trajectories of a protein contained in the sequence data, and show that epistatic interactions continue to enrich in the HIV-1 protease as more potent drugs enter the market.
After revision:  We analyze the "fossils" of the evolutionary trajectories of the protein contained in the sequence data, and show that epistatic interactions continue to enrich in the HIV-1 protease as more potent drugs enter the market.