by applying selective pressure, induce escape mutations in the viral genome. By sequencing the virus from three patients seen before seroconversion, the authors could identify the single founder ...

What was the selective pressure that led to epidermal pigmentation as protection? Skin cancer is unlikely to be a factor, acting too little (in the case of melanoma) or too late in reproductive life.

The dark variety had always existed in small numbers, but only had a selective advantage when the selection pressure changed.

David Merriam is an assistant professor of biology at Metropolitan State University of Denver. He said human transmission of ...