A population geneticist by training, Barbujani has been working on several aspects of human genetic variation.

[1] There are two implications of this finding: first, that most Europeans' ancestors, up to Neolithic times, did not live in geographical Europe, but rather in the Near East; and second, that the early farmers expanding west carried with them their genes, their technologies, and possibly their languages.

His studies of the amount of DNA differentiation among human populations, and of its spatial distribution, led to the conclusion that traditional human racial classifications fail to account for most of the existing patterns of genetic variation.

[2] Rather, it seems that genetic variation is largely uncorrelated across genes, which, if confirmed, would explain why no consensus was ever reached on a catalog of human biological races.

His recent DNA studies focus on genetic characterization of ancient human populations, such as Paleolithic anatomically modern humans of Cro-Magnoid morphology, and groups like the Etruscans[3][4][5] and the Sardinians from the Nuragic era in the Neolithic.