Chris Darwin, 48, who lives in NSW's Blue Mountains, provided a swab from the inside of his cheek to The Genographic Project, which is now collecting similar samples around the world.
His results were unveiled at an event on Thursday at Sydney's Australian Museum, where a related exhibition is open to the public this month.
The analysis showed how Chris Darwin's DNA, and therefore that of his famous forebear, was passed down from people who migrated out of northeast Africa around 45,000 years ago and headed for Europe.
"I think he would be delighted ... and relieved as well," Darwin said referring to one of Charles Darwin's most controversial observations.
Darwin hypothesised in 1871 that modern man came out of Africa, well before the fossil record and modern genetics could offer some supporting evidence.
"He simply looked at the great apes living around the world and the similarities between the chimpanzee and the gorilla were greater with us than the similarities between the orangutan and us," Darwin said.
"He then said, `therefore we must be from Africa' ... he was going right out on a limb.
"It's now pretty conclusive. You can definitely go into denial about it, but you have to deny an awful lot to deny this avalanche of data."
The Genographic Project has collected almost 400,000 DNA samples from volunteers around the world, including about 50,000 from people in remote indigenous communities.
Scientists analyse each DNA sample to reveal parental lineage as well as the presence of different mutations or "markers", said project director Dr Spencer Wells.
"If you share a marker with someone you share an ancestor," Dr Wells said.
"By looking at people from around the world and assessing their patterns of markers, we can build this tree for everybody alive today.
"And we can map where those lineages are found in the world, and that's what we're doing particularly with indigenous and traditional peoples."
This process of pooling and comparing DNA data has also allowed scientists to trace certain mutations back through time to reveal "ancient" genetic patterns and, ultimately, the migratory paths of early man.
"The thing that is confirmed time and time again is this recent `out of Africa' exodus and the idea that we were all African until only about 2000 generations ago," Dr Wells said.
Chris Darwin said his great-great-grandfather could not have foreseen the technological advance that would back his controversial observations.
While the project was focused on detecting tiny genetic differences, Darwin said it also showed how everyone on the planet shared "99.9 per cent" the same DNA.
"So many conflicts in the world are motivated by finding differences between people," he said.
"When you look at this project the differences are so small ... we're all in the same family, and I think that's powerful."
* Members of the public can contribute to the Genographic Project, and learn the history of their genetic code, by purchasing a DNA sample kit ($113). Sales of the kits help to fund language revitalisation and cultural projects in indigenous communities.
