DNA Findings Reveal Genetic History of Humans

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The researchers looked at 10,000 genes in 15 black Americans and 20 European-Americans, all of whom were healthy.

"Across all the individuals, we found almost 40,000 DNA sites that varied. The African-American sample [had] more variations than the European-American sample, which is consistent with previous work showing higher levels of overall genetic diversity in African-Americans," Bustamante said.

This finding suggests that only a subset of diversity was present in the founding populations of Europe, Bustamante said, adding, "We refer to this as a population bottleneck."

Bustamante's team found that the proportion of mutations that are associated with risk for disease is higher in the European-American population. "This is consistent with evolutionary theory that mutations may undergo slightly relaxed natural selection in bottleneck populations," he said.

All the individuals in the study had about 400 mutations that may be linked to disease, Bustamante said.

How these mutations affect human health isn't known, Bustamante added. "Efforts to do sequencing to look at individuals [with] and without disease will likely find rare mutations that may be contributing to disease," he said.

Last month, it was announced that the genomes of 1,000 people worldwide will be mapped in what scientists are calling the most detailed and medically relevant look at human genetic variation ever conducted.

The 1,000 Genomes Project will receive major support from the U.S. National Human Genome Research Institute (NHGRI), the Wellcome Trust Sanger Institute in England, and the Beijing Genomics Institute in China.

"This new project will increase the sensitivity of disease discovery efforts across the genome fivefold and within gene regions at least 10-fold," NHGRI director Dr. Francis S. Collins said in a prepared statement.

More information

For more information on understanding the human genome, visit the Human Genome Project .