Sinek's "Why good leaders make you feel safe"
Sinek, Simon. "Why good leaders make you feel safe." TED. Mar. 2014. TED. Web. 14 Mar. 2016.
In this TED talk, Sinek describes the power of a safe environment to foster trust in a community (n. pag). Sinek gives the example of a military hero who risked his life to save others and said, "they would have done it for me" (n. pag). Sinek argues that this comes from an earlier era, when human tribes banded together in order to better manage and minimize external danger (n. pag).
I could connect this with Matt Ridley's discussion of cooperation in The Origins of Virtue, if I want to take an evolutionary biology approach.