Humans flirt to propagate our genes and to display our genetic worth.
For instance, men flirt with the most healthy, fertile women, who posses biologically correct waist-hip ratios. Women tend to go for men that are well built and have the most resources to invest in them and their children. We flirt as thinking individuals in a particular culture at a particular time, causing the psychology of humans to be more diverse and perverse than the evolutionary determinists would agree with. Humans flirt with conscious calculation and have been known to practice our flirting techniques in front of mirrors. Flirting among humans is biologically driven as well as culturally modulated, it is considered to as much as an art as an instinctive behavior.