When Parker Pennington first saw the embryo, she gasped—but very quietly. At the time, as is often the case for her these days, she had her arm fully inside the rectum of a white rhino, and she didn’t want to alarm the animal by yelping excitedly. In her immersed hand, she held an ultrasound probe, which revealed that the rhino, who goes by Victoria, had a tiny marble in her uterus. She was pregna