TWO STEP HYPOTHESIS 1. “Three hypotheses have been proposed to account for two-step meiosis. The first postulates that two-step meiosis better protects against particular selfish genetic elements that increase their transmission frequencies by sabotaging the meiotic products in which they do not end up (known as ‘sister killers’).”
http://biorxiv.org/content/biorxiv/early/2016/04/28/050831.full.pdf