was receiving millions of European immigrants. In the 21st century, many Black Americans have some degree of European ancestry, while few white Americans have African ancestry. The Brazilian approach to classification by visible features is criticized by geneticist Sérgio Pena: "Only a few genes are responsible for someone's skin colour, which is a very poor indication of ancestry. A white person could have more African genes than a black one or vice versa, especially in a country like Brazil". Sociologist Simon Schwartzman points out that to "substitute negro for preto, suppressing the pardo alternative would mean to impose unto Brazil a vision of the racial issue as a dichotomy, similar to that of the United States, which would not be true." A 2007 study found that White workers received an average monthly income almost twice that of blacks and pardos (browns). The blacks and browns earned on average 1.8 minimum wages, while the whites had a yield of 3.4 minimum wages. Gilberto Freyre has described that few wealthy Brazilians admit to having African ancestry. Affirmative action issue In recent years, the Brazilian government has encouraged affirmative action programs for persons considered to be "African-descendant" and also for Amerindians. This is happening, in part, through the created systems of preferred admissions (quotas) for racial minorities. Other measures include priority in land reform for areas populated by remnants of quilombolas. The government notes that these groups have historically been discriminated against because of slavery and the Portuguese conquest of the indigenous peoples. They became landless and are represented among the poorest segments of Brazilian society, while the European or White population dominates the upper classes. Such efforts in affirmative action have been criticized because of the ambiguity of racial classification in Brazil. Some people have tried to use this system for personal advantage. In 2007, the twin brothers Alex and Alan Teixeira applied for places in the University of Brasília through quotas reserved for "Black students". In the university, a team of specialists and professors used photos of the candidates to determine who was Black or not. The Teixeira brothers were identical twins, but in this process, only Alan was classified as Black, while his identical brother Alex, whose application was reviewed by different people, was not accepted in this program. Since that case, governmental affirmative action programs have been widely criticized. Given the high degree of miscegenation of the Brazilian people,