Spring 2009 IU Behavior Colloquia

Dr. Mark Flinn
Departments of Anthropology and Psychological Sciences at the University of Missouri, Columbia

Hormones and the evolution of the social human brain

THURSDAY, MARCH 5
2:30pm
IMU Dogwood Room
ABSTRACT:
We humans are highly sensitive to our social environments. Our brains have special abilities such as empathy and foresight that allow us to understand each others' feelings and communicate in ways that are unique among all living organisms. Our extraordinary social brains, however, come with some significant strings attached. Our emotional states can be strongly influenced by what others say and do. Our hearts can soar, but they also can be broken. Our bodies use internal messengers -- hormones and neurotransmitters -- to help guide responses to our social worlds. From romantic daydreams to jealous rage, from orgasm to lactation and parent-child bonding, the powerful molecules produced and released by tiny and otherwise seemingly insignificant cells and glands help orchestrate our thoughts and actions.
Here I focus on the question of why stress hormone systems are highly sensitive to social challenges. For example, levels of the glucocorticoid stress hormone cortisol increase acutely in response to a wide variety of social-cognitive demands. Elevation of stress hormones can have short- and long-term health costs, presenting an evolutionary paradox. We do not have good explanations for why there are links between the parts of the brain that assess the social environment and the hormonal systems that control stress hormones such as cortisol and epinephrine (adrenaline). Furthermore, we do not understand why these links are modifiable during child development, such that early experiences may permanently alter hormonal response to social threats.
Hypotheses are evaluated with a review of a 20-year study of child stress in a rural community on the island of Dominica. My limited objective here is to provide a plausible model and some new pieces of the puzzle linking stress response and health outcomes to the neural plasticity that helps us respond to the dynamic human social environment. I conclude with a discussion of the special importance of family relationships in human evolution.

Sponsored by the Center for the Integrative Study of Animal Behavior Hosted by Michael Muehlenbein