It is able to reproduce both with and without a partner - but apparently that has not helped it much either. They were fed a rather scarce amount of the ever-popular yeast staple, glucose, and galactose, a sugar found in milk. Yeast does not normally consider the latter to be a food. A glance at their chaste cultural neighbors showed that they, too, had adapted. So sex with changing partners not only does not prevent extinction, it doesn't even expand the menu.
Real monogamy is a rarity in the animal kingdom.
Only few species go as far as mountain gorillas, where couples stay together their whole lives and males kill the results of any indiscretion on the part of their mates. Apparently, the gorillas' fidelity means an advantage to the married males - their genes get a head start. Social animal partnerships, in which both take care of each other and of the offspring, are more frequently found than such genetic partnerships. The Eastern Bluebird was long considered the romantic Rock of Gibraltar in the wild waters of polygamy. But its reputation has suffered ever since an analysis by Georgia University showed that one in five chicks is clearly NOT the offspring of its doting feathered father.