“How can you side with those people?” In 2002, a paralyzed research advocate who actively supports embryonic-stem-cell and human-cloning research asked me this question. By “those” people she meant Christians, conservatives, and pro-life groups. “It’s simple,” I said. “Why is it in our interest to sit in these wheelchairs for the rest of our lives so science can puzzle over safety problems linked to embryonic stem cells and human cloning, while ignoring the cells that nature designed for the treatments we need?” In the discussion that followed I explained why embryonic stem cells (ESCs) are inferior to adult stem...