Pick up a geography textbook from the first half of this century and you can discover a simple rule-of-thumb explanation for the varying fates of the human race: the weather.
''As a rule, people do their best thinking and planning, their minds are most alert and inventive, and they have the best judgment when the thermometer out of doors falls toward freezing at night and rises toward 50 degrees or 55 degrees by day,'' declares Ellsworth Huntington in ''Principles of Human Geography.'' ''In an invigorating climate'' -- like that of Europe and the northern United States -- ''it may also be easier to be honest and sober and self-controlled than in a more enervating one.''
Such pronouncements ultimately made geographers seem like phrenologists who pondered the size of bumps on a person's skull. Most serious scholars shunted geography aside and forgot it.
Yet after decades of neglect, geography is being rediscovered. The study of how location affects the way people live is not only drawing in new students, it is also attracting the attention of scholars in other fields. Historians, economists and political scientists are using it to explain everything from why some nations are rich and others poor, to why Brazil and Nigeria are rising as regional powers, to why Africa produces so many superior distance runners. It's as if New York City real estate agents were suddenly given the job of explaining some of the globe's most elusive questions and chorused: Location, location, location.
The geographic renaissance, propelled in part by new advances in science and computers, is significant, scholars say, because it is generating a new intellectual dialogue. ''It is a wonderful bridge among disciplines,'' David Landes, professor emeritus of history and economics at Harvard University, said in an interview. ''It compels people to put together ideas they might not otherwise.''
Most unexpected, however, is that the very field that had a racialist taint is now being used to knock down theories that define achievement in racial terms. Geography, once employed to justify colonialism and the innate superiority of whites, is brought in to undermine works like ''The Bell Curve,'' which argues that racial differences in intelligence are inherited and linked to differences in performance and economic success.
The gradual eclipse of geography began 50 years ago when Harvard University eliminated its geography department. The decision had less to do with discomfort over screwball theories (which weren't necessarily seen at the time as screwball) than with academic infighting and weak teaching. ''Geography is not a university subject,'' declared James B. Conant, who was then the president of Harvard.
In the next decades, other universities followed Harvard's lead: Stanford, Yale, the University of Michigan, Columbia, the University of Chicago. According to a report in the Chronicle of Higher Education on the 1987 meeting of the Association of American Geographers, department chairmen organized a seminar ''to find out what they could do to avoid finding their departments on a university hit list.''
Saul Cohen, a political geographer and former president of the geographers' association, says: ''Very few people were exposed to geography who went to college after the 1960's. What they knew about it goes back a half century.''
Quietly Wiped Out As a Discipline
French historians like Fernand Braudel and other members of the Annales school did look at geography, climate and land use. But in the United States, said Mr. Landes, geography was ''a kind of outcast among intellectual disciplines.'' He continued: ''More than any other field I can think of, geography was wiped out kind of quietly. I can't think of another discipline that suffered this sort of erasure.''
Geography was fine if you worked at Rand McNally or played Jeopardy (Moroni. What is the capital of Comoros?). But when American scholars tackled persistent questions like why industrialization first took root in Europe instead of China or India, geography was played down. ''If you look at most works on global development,'' Mr. Landes says, ''there is very little on geography.''
That has been changing. Jared Diamond, a physiologist at the University of California at Los Angeles, combines epidemiology, sociology, zoology, anthropology and botany to conclude that geography is the key to the pace and timing of economic development.
In his book ''Guns, Germs and Steel'' (W.W. Norton, 1997) he goes back 13,000 years to explain how food production is the starting point for success. Because farming communities produce more food and domesticate animals, they can feed non-food producers like professional soldiers, bureaucrats, writers and craftsmen.
Mr. Diamond argues that the east-west axis of Eurasia's land mass meant a shared latitude and similar growing conditions, which enabled one of the first domesticated crops, einkorn wheat, to spread relatively quickly from the Fertile Crescent to Europe; more than twice as fast, for example, as corn and beans spread from Mexico northward to what would become the eastern United States.