During the 1700s, Jean Jacques Rousseau made the distinction between humans and other less evolved animals by noting that we humans possess vanity. That's an important distinction and is still relevant, if not more so, today.

Much of mankind lives in fear of lack of acceptance and approval due to vanity. As such, we are very open to manipulation and negative attitudes towards others. As far as evolution goes, sometimes the animals win since they're not burdened by so many of our human failings.