Coordinated Dancing

What is it about watching a group of people dance in unison that stirs the blood? I just watched the music video for Janet Jackson's song "Feedback," and was struck, again, by how thrilled one can feel by watching group dancing. I wish I knew why I felt this way. Does the feeling stem from early human history, and battle demonstrations? (I have included a video of the New Zealand All Blacks rugby team performing their haka routine for comparison.) Also, the Michael Jackson video below shows how group dancing can be menacing. Interesting....