Sweep = ?

Context:

Subtle Shifts, Not Major Sweeps, Drove Human Evolution
ScienceDaily (Feb. 28, 2011) — The most popular model used by geneticists for the last 35 years to detect the footprints of human evolution may overlook more common subtle changes, a new international study finds.

Classic selective sweeps, when a beneficial genetic mutation quickly spreads through the human population, are thought to have been the primary driver of human evolution. But a new computational analysis, published in the February 18, 2011 issue of Science, reveals that such events may have been rare, with little influence on the history of our species.

By examining the sequences of nearly 200 human genomes, researchers led by Ryan Hernandez, PhD, assistant professor of Bioengineering and Therapeutic Sciences at the University of California at San Francisco, found new evidence arguing against selective sweeps as the dominant mode of human adaptation.