I don’t think there was so much change in the environment in Lenski’s experiment (they are always using the same medium, but the environment may still change because of the organisms inside it evolve). But it’s true that immortality could make people more resistant just because they have young bodies, or some other side-effect reason. That is the case where first-order fitness is large enough to prevail over second-order. I don’t see why the immortality pill would have such a strong effect, though.
I don’t think there was so much change in the environment in Lenski’s experiment (they are always using the same medium, but the environment may still change because of the organisms inside it evolve). But it’s true that immortality could make people more resistant just because they have young bodies, or some other side-effect reason. That is the case where first-order fitness is large enough to prevail over second-order. I don’t see why the immortality pill would have such a strong effect, though.