An elderly population loses social coherence and connections, according to a recent study of one of humanity's closest cousins. Rhesus macaques have been studied for many years in Cayo Santiago or "Monkey Isle" in Puerto Rico. Recent studies revealed that as individuals age, female macaques "actively limit" the size of their social networks and give older connections priority, a behaviour similarly observed in humans. An international team led by the University of Exeter conducted a new study to investigate how this impacts the overall cohesiveness and ties of the social groupings that older monkeys reside in. While social cohesion and connection in the observed macaque populations—which had no more than 20% "old" individuals—were unaffected, computer models suggested that higher numbers of old macaques would weaken those connections. Focusing on close friends and family in later life may provide a number of advantages for both people and macaques, according to Erin Siracusa of Exeter's Centre for Research in Animal Behaviour. "The goal of our study was to determine what impact these individual age-related changes have on how connected a society is as a whole. We had data on six monkey groups that represented a total of 19 social networks that had been gathered over the course of eight years." Siracusa added: "We discovered that older female macaques are poor influencers because they have fewer friends and are therefore less able to share their expertise and experience with those outside of their immediate social networks. The researchers looked at whether monkey networks were less cohesive and connected if there were more elderly females (beyond the age of 18). They found no distinction between networks with a higher proportion of young adults and those with older members in the macaque populations they studied. Yet, in any particular group the researchers studied, no more than 20% of the monkeys were elderly. Even the more dated networks can still be impacted. The researchers therefore developed a computer model to replicate the impact of having more elderly macaques, and they discovered a drop in network cohesiveness and connectivity as a result. According to Professor Lauren Brent, also from the University of Exeter, "We identified extremely considerable effects for network topology, which might affect helpful things like information transfer and cooperation, and could also limit the spread of disease." Brent added: "Ageing of the population in humans is expected to lead to some of the biggest social changes in the 21st century." According to the findings, social structures, cohesion, and connectivity could all undergo major change when the number of people over 60 doubles globally by the year 2050. While the human population is ageing, some animal populations are, on average, getting younger, which could have equally negative effects. A 2021 University of Exeter study discovered that male elephants are more aggressive towards items like tourist cars when fewer older males are around. Older male elephants are frequently targeted by trophy hunters for their enormous tusks.
