Sadness - The Origin of Human Emotion

I'm working on an assignment relating to the brain's cortical structures such as the medial prefrontal cortex and its involvement, together with subcortical structures like the amygdala and the hippocampus, in the realm of emotion and emotion regulation.

I was struck by a passage that I read in a text written by Jonathan H. Turner. It's about the conceptualisation of sadness in terms of brain activity. It offers a social explanation for the role of sadness. It's also about the evolutionary role of sadness for survival. I've highlighted in bold those passages I'm fond of.

...One answer is that sadness is simply a by-product of depression of neurotransmitters, neuroactive peptides, and, as recent imaging studies reveal, underactivation of the subgenual prefrontal cortex (Drevets et al. 1997).

Another answer is that sadness is a very effective mechanism of social control.
For example, guilt and shame are often the outcome when a person senses that they have made others unhappy or sad by not meeting expectations; and so moral codes and comformity to them are built, not just on positive and negative sanctions, but also upon more complex sanctioning practices that avoid the full mobilization of anger.
Sadness is a very effective negative sanction because [..] it does not contain the volatitily of anger-based negative sanctions; and it is effective as a direct sanctioning technique by others, while at the same time, it often evokes sadness in the person who feels that they have failed to meet others' or their own expectations [..]. Thus guilt, shame, and other emotions in which sadness is a dominant componant are probably more than a by-product of suspension of other emotional responses; sadness is a key to social control revolving around negative sanctioning that avoids the volatility of anger and fear, although these latter emotions are part of a complex second-order emotions like shame and guilt. Moreover, sadness is also a signal to others that the individual is in need of social support. By reading signals of sadness, others become aware that a person requires attention and positive emotions. In fact, sadness is a good example of how humans read emotions nonverbally, because we respond most actively to body signals that a person is unhappy. There was probably selection for this kind of response, since, if a group-living animal with strong bioprogrammers for such living is to sustain solidarity, it must be able to read and respond to cues that [other] individuals are not mobilized to put energy into solidarity-maintaining rituals.
- Jonathan H. Turner, On the origins of human emotion: a sociological inquiry into the evolution of human affect, Stanford University Press, 2000

I supposed that people who are adept at dissimulating to others that they are sad often do not receive the social support that they need. It is ironic that such people may believe themselves to be self-sufficient and well-adapted but in fact by refusing to overtly manifest their sadness, they are arguably behaving in a way contrary to what survival dictates.

Meanwhile, I find it interesting how humans, at least those who are pro-social, are wired to interpret any form of 'low activity', 'low social presence', 'withdrawing' in any other individual, as a sign that something is wrong. If they see that an individual is no longer actively engaging in social activities and instead undergoes a period of 'depressed' living, it is then instinctively believed that this person, according to Turner, is unable to mobilize energy into solidarity-maintaining rituals. And in that case, evolutionarily speaking, people tend to think that this person's survival may be threatened and from this realisation stems an attempt by others to support them.

How illuminating!