It’s good to have friends, for humans and chimpanzees. But the nature and number of those friends change over time. In young adulthood, humans tend to have a lot of friendships. But as they age, social circles narrow, and people tend to keep a few good friends around and enjoy them more.
This trend holds across many cultures, and one explanation has to do with awareness of one’s own mortality.
Zarin P. Machanda, an anthropologist at Tufts University, and her own good friend, Alexandra G. Rosati, a psychologist and anthropologist at the University of Michigan, wondered whether chimpanzees, which they both study, would show a similar pattern even though they don’t seem to have anything like a human sense of their own inevitable death.
The idea, in humans, Dr. Machanda said, is that as we get older we think, “I don’t have time for these negative people in my life, or I don’t want to waste my time with all of this negativity.” So we concentrate on a few good friends and invest in them. This explanation is called socioemotional selectivity theory.
Dr. Rosati and Dr. Machanda, who is the director of long-term research at the Kibale Chimpanzee Project in Uganda, drew on many years of observations of chimps at Kibale. Along with several colleagues, they reported Thursday in the journal Science that male chimps, at least, display the very same inclinations as humans. The team looked only at interactions of male chimpanzees because males are quite gregarious and form a lot of friendships, whereas females are more tied to family groups. So male relationships were easier to analyze.
The finding doesn’t prove or disprove anything about whether knowledge of death is what drives the human behavior. But it does show that our closest primate relative displays the same bonding habits for some other reason, perhaps something about aging that the two species have in common. At the very least, the finding raises questions about humans.
Read the full article at the New York Times.
