To be a card-carrying historian of science is to be resolute in one’s determination to avoid present-projecting anachronism in dealing with the scientific past. Even so, an emerging historiographic consensus suggests that, whether we like it or not, some engagement with the scientific present is not merely inescapable but, in certain forms, intellectually and morally wholesome. In my recent book Disputed Inheritance: The Battle over Mendel and the Future of Biology (Chicago, 2023), I have sought to replace the familiar “winner’s history” narrative of the rise of Mendelism in the early twentieth century with a vigorously de-anachronized account. But the scientific present nevertheless pokes through that account at several points and in a number of ways. With help from the taxonomy of presentism proposed by the French historian-philosopher of science Laurent Loison, I’ll offer a practitioner’s reflections on some legitimate roles for present science in the enterprise of describing, explaining, and understanding past science.