Of course, Fisher pooh-poohs polyamory; she's protecting her bottom line. Dr. Helen Fisher helped develop Chemistry.com, a dating site, and is still very much involved in it. I am sure she makes a lot of money from Chemistry.com. The site is very focused on encouraging its members to believe in the dream of finding "The One."
Acknowledging that polyamory can work wouldn't help her profits much when Chemistry.com holds out that golden apple of finding happiness ever after with the one and only prince or princess of your dreams!