I found this article. It's very succinct and well written, highlighting all of the characteristics of the typical alpha male.
Men's and women's flirting body language revealed free. Alpha Male Body language for flirting and dating. Learn body language secrets. Learn how to flirt with a girl. Learn how to flirt with a guy.
I'm a firm believer that our behaviour is heavily influenced by our evolutionary history. Alpha males are a classic example of this.