The Role of Emotions, Cooperation, and Social Relationships in Human Evolution

Emotions are complex psycho-physiological experiences of an individual’s state of mind while interacting with internal and environmental influences. Simply put, emotions are a reaction to internal and external stimuli. While humans express emotions with words most often, non human primates don’t have that luxury. Primates express emotion with facial expressions, postures, grunts, and other physical means. And of course, humans do these things also. The most obvious displays of emotion are caused by another individual’s behavior, like when someone irritates us, makes us sad, happy, etc.

Negative reactions to another’s behavior raise the level of anxiety and insecurity.

Emotions are the result of being part of a society that has conflicts of interest. The stress of relationships in those societies is a source of anxiety because social relationships are important to survival. And anxiety translates into heightened emotions. Emotions evolved in primates because they are powerful tools to prevent and or regulate conflict. When conflict arises, this stimulates the release of cortisol, a hormone associated with stress response, into the body which leads to anxiety and insecurity. Displays of emotion are signals to others, especially in non verbal situations. When one chimpanzee invades the territory of another, the chimp may signal his anger before a physical conflict occurs.

Humans and other primates deal with this added stress by attempting to reconcile, this is often done with physical contact. Emotions are useful in pre-conflict scenarios because they convey important information to the other individual. For example, a dominant male chimpanzee may bare his teeth or grunt at a subordinate male who is encroaching on resources.

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This would let the lower ranked chimpanzee know that he’s on thin ice and another false move may result in a dangerous physical conflict.

If the subordinate chimpanzee acknowledges the signal the conflict can be avoided all together. In post-conflict scenarios emotions are useful because they help mediate the stress levels of both parties involved. If the parties reconcile with physical contact, such as embracing or grooming, the cortisol levels in the body lower at a quicker rate than if there is no reconciliation. The anxiety is also useful because it increases alertness and arousal to prepare the individual for another activity, such as being chased or sexual activity.

Emotions are costly signals because they convey information to another party at a cost to the actor in the form of wasted energy. Emotional displays draw attention and therefore raise the risk of predation. The benefits of expressing the emotions outweigh the cost of potentially being preyed on. Emotional displays may also assist in mating success; females may be likely to choose a male that is more reasonable than violent. A reasonable male would probably survive longer, thereby being better equipped to take care of a family.

Reconciliation is important to the well being of individuals involved in conflicts. Physical contact helps relieve tension by counteracting cortisol levels with endorphins. Reconciliation not only benefits the individuals involved, but the rest of the group also, by relieving the tension. Reconciliation also helps prevent future aggression and the threat of being attacked, which in turn, regulates anxiety levels. Less anxiety then leads to the individual being healthier physically and mentally. Studies show that individuals with strong social relationships have a lower risk of illness, disease, accidents, and mortality.

An individual’s level of anxiety is a reflection on the value of the relationship. Conflicts in relationships that are more valuable than others (i.e. mother-child v. siblings), have the greatest level of anxiety following the conflict. Although, when conflict occurs in high quality relationships it doesn’t usually damage the security of the relationship. In unfamiliar situations quality relationships can act as a buffer by reducing anxiety and insecurity in individuals, as seen in research with guinea pigs.

The inherent side effects of group living include a higher risk for conflicts of interest, so to counteract that, social interactions, cooperation, and negotiation tools such as emotions evolved. In cooperative relationships, individuals should behave in a manner to maintain a good balance not only for themselves, but the other individual in the relationship also. Social interactions that are positive in nature lead to lowered levels of anxiety. When conflicts do arise, reconciliation between those involved is important to the whole group.

Primates are such social creatures that even though only two individuals may be involved in the skirmish, the other members who have connections to the individuals feel the effects of tension. After reconciliation, the relationship may become even stronger because it reduces tension, lessens the chances of continued attacks, and stabilizes the relationship. In some circumstances a third party may intervene before, during, or after the conflict. This behavior reduces tension by deflecting attention or instigating physical contact in the pre-escalation phase. The third party may also catalyze post-conflict contact between the opponents, like when a mother has siblings hug one another after a fight.

I agree with Aureli and Smucny, managing social relationships was and is important to society because without relationships it would be very difficult to survive. Perhaps not so much these days, but our ancestors needed others to look out for each other, especially during foraging. Or in the case of a mother and her child, an infant would not survive without the relationship they share. We see that emotions don’t require advanced intelligence, a large brain, or language in many organisms. Such as with newborn humans, they don’t use intelligence, high brain processes, or language to express how they feel. We discover their emotions by facial expressions, crying, and other physical activities.

Cooperation and social relationships evolved because the benefits of group living outweighed the cost of being solitary and since conflict is greater in groups. In most cases human emotions are not that different from non-human primate emotions. Human emotions are more complicated however, because our brains operate at a higher level of processing. We certainly share all the basic emotions, such as anger, sadness, and happiness. But I think emotions we don’t share with other primates might be jealousy and or romantic love.