Jealousy is commonly known as a negative emotional reaction experienced when a relationship that is important to an individual is threatened by a rival. Perhaps then it is not surprising that jealousy can be viewed as a negative emotion that will only harm relationships. It is viewed as harmful to relationships due to its ability to evoke negative emotions such as anger, fear, and sadness. In addition, the onset of jealousy can occur for many different reasons that are associated with loss of affection, rejection, suspiciousness, insecurity, and anxiety. But, while jealousy can harm relationships, it can also help relationships.
Daly, Wilson, and Weghorst report that human males evolved defenses such as jealousy to protect them against wasting their efforts on children they had not sired. For a woman, jealousy provided a way to ensure that her male partner is investing resources in raising her offspring rather than squandering his resources on other women. Jealousy also evolved to protect love from the threat of loss and the threat of loss to a rival. So, while jealousy can lead to negative emotions, when it is properly used, it can also enhance relationships and provide mating benefits and enhance survival, i.e., it is an adaptive emotion.