researchers were cautious with the results as their samples came from paternity test takers which may have skewed the results partly. São Paulo state, the most populous state in Brazil, with about 40 million people, showed the following composition, according to an autosomal study from 2006: European genes account for 79% of the heritage of the people of São Paulo, 14% are of African origin, and 7% Native American. A more recent study, from 2013, found the following composition in São Paulo state: 61,9% European, 25,5% African and 11,6% Native American. Several other older studies have suggested that European ancestry is the main component in all Brazilian regions. A study from 1965, "Methods of Analysis of a Hybrid Population" (Human Biology, vol. 37, no. 1), led by the geneticists D. F. Roberts and R. W. Hiorns, found out the average the Northeastern Brazilian to be predominantly European in ancestry (65%), with minor but important African and Native American contributions (25% and 9%). A study from 2002 quoted previous and older studies (28. Salzano F. M. Interciêência. 1997;22:221–227. 29. Santos S. E. B., Guerreiro J. F. Braz J. Genet. 1995;18:311–315. 30. Dornelles C. L, Callegari-Jacques S. M, Robinson W. M., Weimer T. A., Franco M. H. L. P., Hickmann A. C., Geiger C. J., Salzamo F. M. Genet. Mol. Biol. 1999;22:151–161. 31. Krieger H., Morton N. E., Mi M. P, Azevedo E., Freire-Maia A., Yasuda N. Ann. Hum. Genet. 1965;29:113–125. [PubMed]), saying that: "Salzano (28, a study from 1997) calculated for the Northeastern population as a whole, 51% European, 36% African, and 13% Amerindian ancestries whereas in the north, Santos and Guerreiro (29, a study from 1995) obtained 47% European, 12% African, and 41% Amerindian descent, and in the southernmost state of Rio Grande do Sul, Dornelles et al. (30, a study from 1999) calculated 82% European, 7% African, and 11% Amerindian ancestries. Krieger et al. (31, a study from 1965) studied a population of Brazilian northeastern origin living in São Paulo with blood groups and electrophoretic markers and showed that whites presented 18% of African and 12% of Amerindian genetic contribution and that blacks presented 28% of European and 5% of Amerindian genetic contribution (31). Of course, all of these Amerindian admixture estimates are subject to the caveat mentioned in the previous paragraph. At any rate, compared with these previous studies, our estimates showed higher levels of bidirectional admixture between