They hunt with bows carved from wood, use short poisonous arrows, and speak in a click language that is the oldest human language in the world.
Now, an international team of scientists led by Singapore has proven that one of humanity's oldest "pristine" branches lies within the Southern African Khoisan people.
Since the birth of modern man some 200,000 years ago, a group of the Khoisan have married only within its tribes for the past 150,000 years, isolating itself genetically from the rest of the world.
The ground-breaking discovery upends conventional wisdom that all people today are the result of human groups mixing with one another over hundreds of thousands of years, said Nanyang Technological University's (NTU) Dr Stephan Schuster, who led the research.
"Khoisan hunter-gatherers in Southern Africa have always perceived themselves as the oldest people," he said.
The study, published in Nature Communications last week, makes it official, noted Dr Kim Hie Lim, an NTU senior research fellow.
The six scientists from Singapore, Brazil and the United States made the breakthrough after sequencing the genomes, or genetic make-up, of five living Khoisan tribesmen.
For two of them, the results were unlike anything seen in the DNA of Europeans, Asians and all other African ethnic groups.
Even after looking at the genomes of 1,462 people from 48 ethnic groups worldwide, the scientists found no evidence that these two Khoisan members' ancestors had mixed with any of the groups.
As for the other three Khoisan people whose genomes were not as pristine, Dr Schuster believes they must have had ancestors who married non-Khoisan neighbours, such as the nearby Bantu tribes.
This intermarrying between the non-Khoisan and Khoisan is believed to have occurred within only the last 3,000 years, based on recent genetic studies, he added.
According to the scientists, there are likely only about 100,000 people left whose pristine Khoisan lineage harks back 150,000 years, a minuscule fraction of the seven billion people globally.
But they will have an enormous impact on research into human history.
The high-quality genome sequences obtained from the Khoisan tribesmen will help researchers better understand human population history, especially that of understudied branches such as the Khoisan.
By comparing the genetic sequences of modern ethnic groups to those of the "pristine" Khoisan, for example, scientists can trace each group's ancestral lineage.