The Evolutionary Basis for Human Tolerance – Physiological Responses

For most animals, unfamiliar members of other groups present more of a threat than an opportunity, and are best avoided or even attacked. In contrast, our attitudes are markedly different. There is no denying that we are capable of being hostile to people we do not know, particularly if we feel anxious or threatened. However, compared to other animals, we are unusually open to new relationships, and form strong bonds with individuals outside our family group.

Although we tend to focus on the ‘thinking’ part of our minds, or our cognitive appraisal of social situations, our physiological responses and emotional reactions play a central role in how we build and maintain relationships. Subtle changes in ‘gut feelings’ can have an important influence on our attitudes to people around us, particularly to unfamiliar outsiders or people we have not seen for some time.

An understanding of how different hormones affect social behaviour in other species, as well as in humans, provides insights into the type of changes that led to increasing human ‘friendliness’. Genetic and anatomical evidence documents subtle changes in neuroendocrine function in recent human evolution after 300,000 years ago that appear to have played an important role in increasing tolerance of unfamiliarity, and abilities to forge new external bonds. Being able to make external connections, and form new relationships based on give and take despite lengthy periods apart, seems to have been important to our success as a species. Friends in distant communities may often have been important to survival by providing resources or help that could buffer the effects of crises and resource shortfalls. We find that it is genuine emotional commitments to distant friends, rather than strategic alliances, that allow modern hunter-gatherers to survive in times of crisis.

Changes in emotional dispositions towards being less aggressive and more tolerant of unfamiliar individuals might seem to be progress, but we should be cautious in thinking in these terms. Increased ‘friendliness’ is not without its disadvantages. It also brings downsides in terms of social sensitivities and emotional vulnerabilities that influence much of human behaviour.