The evolution of the adolescent growth spurt: Urinary biomarkers of bone turnover in wild chimpanzees (Pan troglodytes).

Life history theory addresses how organisms balance development and reproduction. Mammals usually invest considerable energy into growth in infancy, and they do so incrementally less until reaching adult body size, when they shift energy to reproduction. Humans are unusual in having a long adolescence when energy is invested in both reproduction and growth, including rapid skeletal growth around puberty.

Puberty initiates a unique stage of social learning and development prior to adulthood: Insights from studies of adolescence in wild chimpanzees.

In humans, puberty initiates a period of rapid growth, change, and formative neurobehavioral development. Brain and behavior changes during this maturational window contribute to opportunities for social learning. Here we provide new insights into adolescence as a unique period of social learning and development by describing field studies of our closest living relatives, chimpanzees.

Viruses associated with ill health in wild chimpanzees.

Viral infection is a major cause of ill health in wild chimpanzees (Pan troglodytes), but most evidence to date has come from conspicuous disease outbreaks with high morbidity and mortality. To examine the relationship between viral infection and ill health during periods not associated with disease outbreaks, we conducted a longitudinal study of wild eastern chimpanzees (P. t.

A preliminary analysis of wound care and other-regarding behavior in wild chimpanzees at Ngogo, Kibale National Park, Uganda.

Caring for others is a key feature of human behavior. Mothers, fathers, siblings, grandparents, and other group members provide care in the form of provisioning, protection, and first aid. To what extent is other-regarding behavior present in our primate relatives? Here we describe an unusual incident of other-regarding behavior toward an injured juvenile female chimpanzee (Pan troglodytes schweinfurthii) at Ngogo in Kibale National Park, Uganda.

The development of affiliative and coercive reproductive tactics in male chimpanzees.

Like many animals, adult male chimpanzees often compete for a limited number of mates. They fight other males as they strive for status that confers reproductive benefits and use aggression to coerce females to mate with them. Nevertheless, small-bodied, socially immature adolescent male chimpanzees, who cannot compete with older males for status nor intimidate females, father offspring.

Adolescent and young adult male chimpanzees form affiliative, yet aggressive, relationships with females.

Primates frequently form affiliative relationships that have important fitness consequences. Affiliative relationships between unrelated males and females are ubiquitous in humans but are not widely reported in humans' closest living relatives, chimpanzees (Pan troglodytes). Instead, adult male chimpanzees are extremely aggressive to females, using the aggression to coerce females to mate with them.

Caregiving relationships as evolutionary and developmental bases of obligation.

Obligation as defined by Tomasello requires mutually capable parties, but one-sided caregiver relationships reveal its developmental and evolutionary precursors. Specifically, "coercive" emotions may prompt protective action by caregivers toward infant primates, and infants show distress toward caregivers when they appear to violate expectations in their relationships. We argue that these early social-relational expectations and emotions may form the base of obligation.

Social relationships and caregiving behavior between recently orphaned chimpanzee siblings.

When their mothers die, chimpanzees often adopt younger vulnerable siblings who survive with their care. This phenomenon has been widely reported, but few studies provide details regarding how sibling relationships change immediately following the deaths of their mothers. A disease outbreak that killed several females at Ngogo in Kibale National Park, Uganda, furnished an opportunity to document how maternal death influenced the social relationships of siblings.

Simultaneous outbreaks of respiratory disease in wild chimpanzees caused by distinct viruses of human origin.

Respiratory viruses of human origin infect wild apes across Africa, sometimes lethally. Here we report simultaneous outbreaks of two distinct human respiratory viruses, human metapneumovirus (MPV; Pneumoviridae: Metapneumovirus) and human respirovirus 3 (HRV3; Paramyxoviridae; Respirovirus, formerly known as parainfluenza virus 3), in two chimpanzee (Pan troglodytes schweinfurthii) communities in the same forest in Uganda in December 2016 and January 2017. The viruses were absent before the outbreaks, but each was present in ill chimpanzees from one community during the outbreak period.

Adolescent male chimpanzees do not form a dominance hierarchy with their peers.

Dominance hierarchies are a prominent feature of the lives of many primate species. These hierarchies have important fitness consequences, as high rank is often positively correlated with reproduction. Although adult male chimpanzees strive for status to gain fitness benefits, the development of dominance relationships is not well understood.

No evidence for contagious yawning in lemurs.

Among some haplorhine primates, including humans, relaxed yawns spread contagiously. Such contagious yawning has been linked to social bonds and empathy in some species. However, no studies have investigated contagious yawning in strepsirhines.

The evolution of self-control.

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations.

Group Size Predicts Social but Not Nonsocial Cognition in Lemurs.

The social intelligence hypothesis suggests that living in large social networks was the primary selective pressure for the evolution of complex cognition in primates. This hypothesis is supported by comparative studies demonstrating a positive relationship between social group size and relative brain size across primates. However, the relationship between brain size and cognition remains equivocal.