Most major biological molecules, including all proteins, DNA and RNA, point in one direction or another. In other words, they are chiral, or handed. Like how your left glove fits only your left hand and your right glove your right hand, chiral molecules can interact only with other molecules of compatible handedness.
Given enough time, a fitness-neutral variant will tend to fixation due to drift alone, unless there are density-dependent effects (i.e., unless being relatively rare increases fitness). The article is concerned that there may be some such effect, but the extinction of any primordial chiral life suggests that there isn’t.