[WS:] I think you are downplaying the importance of mirror neurons and the behavior they enable. Mirror neurons are essential in developing empathy - which is considered the most "human" of all emotions. Arguably, empathy is the foundation of all social organization and social solidarity. Without empathy, you would essentially have that heaven of neoliberalism, a "market society" - aka Jeder für sich und Gott gegen alle http://www.imdb.com/title/tt0071691/
^^^^^ CB; However ,if you notice, monkeys have mirror neurons. The study in question is about monkeys ,not humans. Therefore, if the mirror neuron is the basis for empathy, then monkeys would have as much empathy as humans, and that would contradict your assertion that empathy is "the most _human_ of all emotions", since monkeys would have it too.
Monkey see, monkey do: Mirror neuron in monkeys might explain the famous monkey ability to imitate.
So, what it unique in human social organization and social solidarity is humans' ability to relate "socially" to a wider group of their species than other primates like chimps and monkeys. It's not that other primates are not social, it is that humans extend that sociality even further. This wider group is across both time and space. I emphasize the social "solidarity" across time. Note that the ancestors reach forward in time, as well as the descendents reaching back in time. The invention of culture occurred when some hominids thought "lets communicate with future generations. How can we pass messages on to our future descendents".