Before abolition, the growth of the black population was mainly due to the acquisition of new slaves from Africa. In Brazil, the black population had a negative growth. This was due to the low life expectancy of the slaves, which was around seven years. It was also because of the imbalance between the number of men and women. The vast majority of slaves were men, black women being a minority. Slaves rarely had a family and the unions between the slaves was hampered due to incessant hours of work. Another very important factor was that black women were held by white and mixed-race men. The Portuguese colonization, largely composed of men with very few women resulted in a social context in which white men disputed indigenous or African women. According to Gilberto Freyre, in colonial Brazilian society the few African women who arrived quickly became concubines, and in some cases, officially wives of the Portuguese settlers. In large plantations of sugar cane and in the mining areas, the white master often choose the most beautiful black slaves to work inside the house. These slaves were raped by their masters, producing a very large Mulato population. The diplomat and ethnologist Richard Burton wrote that "Mulatism became a necessary evil" in the captaincies in the interior of Brazil. He noticed a "strange aversion to marriage" in the 19th century Minas Gerais, arguing that the colonists preferred to have quick relationships with black slaves rather than a marriage.