incomplete sweep
Nielsen R, Hellmann I, Hubisz M, Bustamante C & Clark AG 2007 Recent and ongoing selection in the human genome. Nat Rev Genet 8:857-868.
- much interest has focused on identifying incomplete selective sweeps, which are seen when positively selected mutations are currently on the rise in the human populations but have not yet reached a frequency of 100%
- one of the most famous examples of an incomplete sweep is that at the lactase (LCT) locus in European populations
- lactase persistence is thought to have increased in frequency as a result of positive selection during the past 10,000 years after the emergence of dairy farming
- some African populations that use dairy farming also carry a high-frequency long-range haplotype associated with lactase persistence
- the mutation is distinct from the one observed in Europeans
- another gene that shows almost as strong evidence for an incomplete selective sweep is the glucose-6-phosphate dehydrogenase gene (G6PD)
- almost 30 years ago, Gould and Lewontin76 launched a crusade against the adaptive paradigm that functional differences must be adaptive
- that is, caused by natural selection
- a new generation of biologists with a background in genomics, molecular biology or bioinformatics has taken leadership in the field of genomic evolutionary biology
- the old lessons from Gould and Lewontin76 seem to have been forgotten
- it is a desirable addition to a story of selection to identify possible functional reasons why selection might be acting
- it will never be a method for identifying or verifying selection
