Genome study reveals evidence of natural selection occurring during slavery

Genome study reveals evidence of natural selection occurring during slavery

Scientists probing the genetic makeup of African-Americans say they have found evidence that their early ancestors experienced natural selection as they adapted to the harsh conditions of life in America. "Li Jin of the Chinese Academy of Sciences in Shanghai ":http://www.hugo-international.org/UploadImage/profile14.pdf led the team of researchers who conducted a recent study that illuminated this unexplored area. Since most research studies on the variant genes that cause diseases are conducted on people of European ancestry, the Shanghai team studied the genomes of the earliest African-Americans to ensure that variants specific to this group could be discovered. The study may contribute to the development of treatments and enhanced disease diagnosis, according to the Shanghai team. The researchers used a method for studying admixture, the genetic phenomenon that occurs when two populations or races mix. By using gene chips (a technique that allows scientists to parse DNA sequences in large amounts), the Shanghai researchers were able to deconstruct the composition of the chromosomes of the first Africans to arrive in America and their immediate ancestors. In addition, modern African populations, such as the Yoruba, were studied to compare differences between blacks of today and the likely genetic makeup of their antecedents. Researchers found that of the African-American genomes in their sample, only 22 percent of the DNA analyzed came from Europeans. The remaining DNA was found to come from purely African ancestors, a finding in alignment with previous discoveries. The main result of the study was that "certain disease-causing variant genes were found":http://www.nytimes.com/2012/01/03/science/genome-research-points-to-adaptation-among-early-african-americans.html?pagewanted=all to have become more common in African-Americans after their ancestors reached American shores -- possibly because they presented greater benefits, according to an article published by the team in Genome Research. Additionally, the researchers found that other gene variants have actually become less common over time in African-Americans. For example, the gene for sickle cell hemoglobin -- which protects against malaria when a carrier has two copies of the gene -- has become less common in African-Americans than native Africans, possible because malaria was less of a threat on America's shores. Interestingly, the new gene variants that African-Americans acquired in America are connected with higher risks for hypertension, prostate cancer, sclerosis, and bladder cancer. The researchers assert in their paper that these disease-causing genes may have played an adaptive role for blacks in their new home country. "Most of the genes associated with African-American ethnic diseases may have played an important role in African-Americans' adaptation to local environment," they stated in their paper. However, the authors have not been able to identify the specific benefits these genes may have conferred to the ancestors of modern blacks.