Friendship is the single most important factor influencing our health, well-being, and
happiness. Creating and maintaining friendships is, however, extremely costly, in terms of …

Recent data suggest that the human body is not such a neatly self-sufficient island after all. It
is more like a super-complex ecosystem containing trillions of bacteria and other …

Longevity is a major component of variation in fitness in long-lived iteroparous species [1–4].
Among female baboons, variation in breeding lifespan accounts for approximately 50% of …

Never before have we experienced social isolation on such a massive scale as we have in
response to coronavirus disease 2019 (COVID-19). However, we know that the social …

Convergent evidence from many species reveals the evolutionary origins of human
friendship. In horses, elephants, hyenas, dolphins, monkeys, and chimpanzees, some …

In humans and obligatory social animals, individuals with weak social ties experience
negative health and fitness consequences. The social buffering hypothesis conceptualizes …

Sociality has evolved in many animal taxa, but primates are unusual because they establish
highly differentiated bonds with other group members. Such bonds are particularly …

Psychological studies of relationships tend to focus on specific types of close personal
relationships (romantic, parent–offspring, friendship) and examine characteristics of both the …

In many social mammals, females who form close, differentiated bonds with others
experience greater offspring survival and longevity. We still know little, however, about how …

Glucocorticoids are hormones that mediate the energetic demands that accompany
environmental challenges. It is therefore not surprising that these metabolic hormones have …