Six years ago, Charles C. Mann's "1491" presented a picture of the Americas just before their discovery by Columbus and the scouring of their inhabitants by imported diseases. It was a populated and managed land, much different from the virgin world described by the pioneers.

Now comes a second book, "1493" (Knopf, 544 pp., $30.50). It is about the consequences of the conquest, most of which the reader might not have thought of.

The Irish potato famine, for example: The potato was from the Americas. Before Columbus, no European had eaten a potato.

The lowly tuber is supremely efficient in transforming dirt into calories. Despite the famine, in general the potato allowed more Europeans to survive. "The potato," Mann writes, "fueled the rise of the West" and may have been "as important to the modern era as, say, the invention of the steam engine."

China adopted the sweet potato, which was also from the Americas. The consequences were different. Though the sweet potato helped China get through the Little Ice Age famines of the 1580s and 1590s, it also, Mann writes, "helped kick out the underpinnings of the Ming dynasty," a hidebound regime that was unprepared for a population boom.

This is a book that paints its history in the colors of social science. Like Mann's earlier book, it is academic work popularized. Mann has extracted the story of the spread of non-native species, for example, from Alfred Crosby's "The Columbian Exchange."

Some of those species were microbes. In "1491," Mann told how smallpox wiped out most of the original Americans. In "1493," he argues that malaria was the main reason the English colonists brought Africans to North America to work the Southern plantations. The English had little resistance to the type of malaria prevalent there. The Africans had some immunity to it.

There are economic stories. Under the Tangs, China had created the world's first paper money, and by the time of the Mings, had discovered the downside of printing. After the Spanish found silver in Bolivia, much of it was traded to China, Mann writes, "to replace the paper notes that the government had made valueless." That trade — silver for silk and porcelain — built the city of Manila and put the name of a Spanish king on an Asian nation: the Philippines.

In China, some of the silver was used to pay for work on the Great Wall.

Mann's new book is different from his earlier volume. The year 1491 was an end point, and neatly delineates a book made of limited source material. But 1493 is a starting point that leaves Mann free to follow whatever threads he likes. The result is a book that cannot be comprehensive and doesn't try.

There is a story, for example, of the Europeans' amazement at seeing the first sports team from America with a rubber ball, and, three centuries later, the struggle of "a bankrupt businessman named Charles Goodyear" to make rubber useful. There is a section on the guano islands of Peru. There is the story of the finding of the first pesticide to kill the Colorado potato beetle.

All in a book that starts with Columbus.

Bruce Ramsey (bramsey@seattletimes.com) is a Seattle Times editorial writer.