According to a new study, grandmothers are one of the major reasons why grandchildren become monogamous mates and have long lifespans.

In a finding published in the Proceedings of the National Academy of Science, grandmothers should be given thanks when their grandkids are enjoying a faithful relationship with their partners in addition to long lives.

The "Grandmother Hypothesis" is said to be the reason why grandmas are behind this theory. According to Kristen Hawke, an anthropologist of University of Utah, the hypothesis suggests that grandmothers are the role-players why their grandchildren are living longer lives. They are also one of the major contributor of romantic relationship between lifetime partners.

The study proposed by Hawke was based on her genuine findings of the Hazda hunger-gatherer people in Tanzania. In her observation, it was notable that the older women in the tribe were spending more days collecting foods for their grandchildren. On the other hand, all other mammals and primates are gathering foods for their own after they are done weaning.

 Using a computer model, Hawke then suggests that grandmas are feeding their grandchildren even after weaning in order for daughters to reproduce more children at smaller intervals. She then said that those long living grandmas handed down their longevity genes to their offsprings.

Furthermore, the study implies that grandmothers promote healthy relationship between male and female. In her current study which covers mammals and the early people million years ago, Hawke suggest that whenever "grandmothering" is present at that time, male to female ratio is significantly higher with an average of 111 males for 1 female.

Dr. Peter Kim, the co-author of the study from the Unversity of Sydney proposed that the imbalanced ratio produced an increased competition in finding mates. Whenever a man finds a mate, he then tries to guard her from other rivals which produced monogamy and pair bond.