"Whether it's the fear of being the odd person out, whether it's the fear of uncertainty or the fear of losing your shirt in the market, the fear starts to compel you to do something, because a million years ago, that fear meant you probably had to run or fight," Berns said.

But reactions that saved our ancestors from saber-toothed tigers don't make as much sense on the floor of the Stock Exchange.

Financial historian Jeff Madrick says that's how we got into trouble in the first place - by developing the notion that the stock is highly rational. "That encouraged this herd behavior," he said. "People would say, 'The stock market is right. Let's get in here.' That was the mythology that fed the herd behavior."

So the group think that helped build the bubble is now leading the charge to pop it.

"I think there's probably a panic now," Madrick said. Berns agreed: "You could call it panic; I would."

But the Bronx Zoo's Pat Thomas says, "It's definitely a survival mechanism."

"The group think that helped build the bubble is now leading the charge to pop it."
I popped too. Does that mean I'll be(come) part of the herd and if so, which one and which direction are we going?

Herman Hesse wrote about this in his early works before The Great wars...he was so worried about the German Herd that he moved to Switzerland/N. Italy. See Demian, Steppenwolf.