They hope to sample 100,000 people or more and look for ancient clues buried in living DNA to calculate who came from where and when.
And for $100, anyone who wants to can supply his or her own cheek swab for a personalised analysis and perhaps to contribute to the research.
"We all came out of Africa, but how did we get to where we are today?" asked geneticist and anthropologist Spencer Wells on Wednesday.
"What we are aiming for is the story of everybody."
Experts in related fields such as population genetics, archaeology, evolution science, linguistics and palaeontology will help in the five-year project.
Fossils provide some clues about where people settled as they evolved and moved from Africa to colonise every continent except Antarctica.
But mysteries remain, for example, about how people first got to Australia 50,000 to 60,000 years ago, or when and from where the first humans arrived in the Americas.
"We all came out of Africa, but how did we get to where we
geneticist and anthropologist
Linguistics and DNA provide many clues, but the Genographic Project will aim to systematically look at all peoples on all continents.
Teams in China, Russia, India, Lebanon, Brazil, South Africa, Paris, Britain and Australia have signed on to help.
IBM will provide computers and technical equipment, and the philanthropic Waitt Family Foundation, established by the founder of Gateway computers, will fund field research.
Some groups may be hostile to the effort, Wells said in a telephone interview. "There has been a history of exploitation of indigenous groups around the world," he said.
But experts on dealing with various groups will help sell the idea, Wells said. "It's a question of explaining the science," he said.
Geneticists will look at little changes in DNA code that have been used by experts to trace human history.
Africa is believed to be the home
of an ancient ancestral Eve
Mitochondrial DNA, handed down virtually unchanged from mothers to their children, is one source that was used to calculate the so-called ancestral Eve, who would have lived in Africa about 180,000 years ago.
Men have their own version, found in the Y chromosome, which is inherited with very little change from father to son.
Tiny mistakes in the code that occur with each generation can be used as a kind of genetic clock to track backwards.
People who buy the swab kit are unlikely to add to the indigenous people's database, but can find out something about their own ancient ancestry and perhaps add to the effort, Wells said.