The Nature of Monkeys and Mothering

BREAKTHROUGH RESEARCH SHOWS HOW GENES AND EXPERIENCEFORM DISTINCT PERSONALITIES IN PRIMATES

For millennia, humankind has grown up in social groups with all the rich experiences that such a life entails, But humans aren't the only primates whose individual behaviors are influenced by family members and peers Stephen J, Suomi, Ph. D., chief of the Laboratory of Comparative Ethology at the National Institute of Child, Health and Human Development, explores the intricate interactions between nature and nurture that guide infant development in rhesus monkeys, one of our closest primate relatives,

Nancy K. Dess: What sort of creature is a rhesus monkey?

Stephen J. Suomi: Rhesus monkeys share about 94% of their genes with humans. Second to us, they are the most successful primate species in the world, living together in large numbers over a huge geographic range of snowy, tropical and arid conditions.

NKD: What are the lives of young rhesus like?

SJS: They grow up in complex communities of 30 to several hundred monkeys. These "troops" consist of multigenerational families that are headed by females--females remain in their natal troop for life. Males, on the other hand, stay until they reach puberty, then leave, spend time in all-male gangs and finally join another troop.

NKD: Who raises a young rhesus?

SJS: Virtually all of the parenting is done by the biological mother. When other adults are involved, they are usually female relatives of the biological mother.

NKD: What are some of the differences you see among the youngsters?

SJS: Rhesus have distinctive personalities, ranging from individuals who are very sociable to wallflowers, and from individuals who are meek and mild to those who are extremely aggressive.

NKD: Where do these characteristics come from?

SJS: They appear very early in life and, in general, are remarkably stable into adulthood. This points to a genetic influence. However, while some are born with certain predispositions, these predispositions can be altered substantially by early experiences--especially social experiences with mothers.

NKD: So monkey mothering matters.

SJS: Yes. After their first child, rhesus mothers settle down to a consistent mothering style. Some are more punitive while others are more tolerant of their infant's demands. To study how maternal style affects development, we can identify an infant who is predisposed to shyness or impulsive aggressiveness based on their pedigree. We then foster the infant at one week of age to an unrelated female with a particular maternal style. We have found, for instance, that rhesus genetically predisposed to extreme shyness and reared by an especially tolerant foster mother have above-average peer relations.

NKD: How do shy young raised by tolerant moms make out as parents?

SJS: Young females reared by foster mothers tend to adopt the maternal style of their foster mothers. The best predictor of a monkey's maternal style is the style that she experienced while growing up.

NKD: Maybe these "at-risk" babies who be come socially adept hold a clue as to why apparently "bad" genes persist.

SJS: Perhaps. Our data show that a characteristic that acts as a "risk" factor under some circumstances can be advantageous under others. Rhesus and some other primates live in such a wide variety of environments that no single developmental outcome is going to be optimal in all conditions.

NKD: Lately, the news is rampant with cloning, especially with the Human Genome Project. I've even heard that someone is developing a service to clone pets so that people can have the same pet over and over again. The message seems to be, "It's all in the genes"

SJS: Clearly, genes are not destiny, only predisposition at most. Simple notions of nature "versus" nurture or genes "versus" environment are narrow-minded. Development in all species results from the interaction between both genes and the environment. We should try to avoid genetic value judgments and ideas such as eliminating genes that program "bad" behavioral outcomes. Because in the right circumstances, such genes might be expressed in wonderful ways that we have yet to discover.

PHOTO (BLACK & WHITE): Stephen J. Suomi

Nancy K. Dess is a professor of psychology at Occidental College and senior scientist at the American Psychological Association in Washington, D.C.