“With best friendship there tends to be intimacy, a feeling that the other person is there for you, that they have your back,” says Rebecca Graber, a psychology lecturer at the University of Sussex, in the UK. “It’s about perceived support rather than actually showing up.” However, are we pre-programmed to have best friends?

According to research, there are considerable evolutionary benefits to forming such tight social relationships with others. However, the nature of such ties can vary greatly, and knowing this diversity can provide a great deal of comfort and hope to people looking for a best friend but having difficulty finding one. Dolphins, like humans, create friendships based on common interests. In a 2019 study, male dolphins who forage for food in deep seas, a habit is known as “sponging,” mostly engage with fellow male spongers. Manuela Bizzozzero, a researcher at the University of Zurich and the study’s primary author, explains that these deep ties can survive for decades and are crucial to each male’s mating success. Friendships among female adult baboons enhanced the survival probability of their children, according to a 2003 study led by Princeton University primatologist Jeanne Altmann. Another study found that baboons with strong social links are less stressed and that when a close companion is murdered by predators, females attempt to form new associations.

“The best bang for your buck is to have good friends; it helps you fight off the lions,” says Lydia Denworth, author of the book Friendship, “We also need help fighting off the lions and that’s what our friends do for us.”