Columbus' actions "greatest event in the history of life since the death of the dinosaurs"

How did Christopher Columbus really change history? Not by the "discovery" of the New world, but by ecological convulsion, the exchange of plants, animals and diseases between the two continents. Such is the premise of Charles C. Mann's new book 1493.

"There's absolutely nothing in my garden that originated within 1,000 miles of my house," says Mann. "Tomatoes originated in Mexico. Basil came from Italy. Onions came from Europe. I live in Massachusetts. There's absolutely nothing in there from New England."

The NPR program Fresh Air from WHYY interviews the author of 1493: Uncovering the New World Columbus Created in both print and audio versions.