evolutionary roots of friending

Non-human animals can have quite complex social relationships.  Consider, for example, greylag geese.  They live in flocks.  Within a flock, the geese recognize closely related birds (kin) long past the period of necessary care for dependent offspring. In addition, the geese form long-term, opposite-sex, reproductive pair-bonds.  The geese identify close genetic relations (kin) with a much more genetically distant other (the reproductive partner) as a behavioral category of affiliated flock members.  Among affiliated flock members, almost no aggression occurs. Among non-affiliated flock members, aggression is frequent.[1]

The geese have sensitive physiological responses to social events. Aggressive  interactions or geese taking off or landing (social events) occur more frequently and predictably than vehicles passing by or loud noises (non-social events). A goose’s heart rate, however, increases significantly more when it observes the social events than when it observes the non-social events.  Moreover, a goose’s heart rate increases significantly more when it observes an aggressive interaction involving an affiliated goose than when it observes an aggressive interaction involving unaffiliated geese. Geese are thus emotionally sensitive to the occurrence of and participants in social events that do not directly involve them.[2]

Wild baboons also have complex social relationships. Like at least some ancient human populations, female baboons remain in their natal group and male baboons disperse. Adult male baboons within a group  form a dominance hierarchy with high mating skew.  Events closely associated with male baboons’ reproductive fitness (changes in the male dominance hierarchy and sexual consorting) produce a physiological indicator of stress.  A male’s position in the male dominance hierarchy is correlated with his level of stress.[3]

Compared to males, female baboons’ sources of stress are more closely associated with social relations.  While females form dominance hierarchies, females have much less mating skew than do males, and a female’s position in the female dominance hierarchy is not correlated with her level of stress.  Females also are more active in forming and maintaining social relations.  Consistent with that social orientation, females seem to use grooming to reduce stress.  Although a female may groom at some time with all other females in her group, females typically groom mainly with a few predictable partners.  Those partners often are close female kin.  Females with greater dispersion in their grooming partner-time have higher stress.  If one of a female’s primary grooming partners dies, she suffers stress and increases her dispersion in grooming partners.  That’s reasonably interpreted as behavior oriented toward finding a suitable, new primary grooming partner.[4]

Language and complex cognition aren’t necessary for complex social relations.  Social relations among non-human animals are similar in important respects to those of humans.  If you want to understand Facebook better, study geese and baboons.



[1] Claudia A. F. Wascher, , Isabella B. R. Scheiber and Kurt Kotrschal, “Heart rate modulation in bystanding geese watching social and non-social events,” Proceedings of the Royal Society B, 2008, 275, 1653-1659 (doi:10.1098/rspb.2008.0146).  Young greylag geese remain with their parents for one year or more after fledging.

[2] Id.  Information on the geese’s heart rates were transmitted from fully implanted radio transmitters.

[3] The ancient Hebrews apparently had a system of  female philopatry and male dispersal.  See Genesis 2:24.  On male baboons, see T. J. Bergman, J. C. Beehner, D. L. Cheney, R. M. Seyfarth and P. L. Whitten, “Correlates of stress in free-ranging male chacma baboons, Papio hamadryas ursinus,” Animal Behaviour, 2005, 70, 703–713 (doi:10.1016/j.anbehav.2004.12.017).  The physiological indicator of stress is elevated glucocorticoid level.  All subsequent references to increased stress are based on this indicator.  The direction of correlation between male rank and stress level depends on specific social circumstances.

[4] Catherine Crockford, Roman M. Wittig, Patricia L. Whitten, Robert M. Seyfarth, Dorothy L. Cheney, “Social stressors and coping mechanisms in wild female baboons (Papio hamadryas ursinus),” Hormones and Behavior, 2008, 53, 254–265.

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