One of the first protein polymorphisms identified in humans involves alternative forms of haptoglobin, one of the most abundant proteins in the blood. The genetic origins and medical significance of this variation have puzzled scientists since its discovery. Now, a team of researchers from the Broad Institute’s Medical and Population Genetics Program led by institute member Steve McCarroll and postdoctoral associate Linda Boettger has revealed that haptoglobin variation likely arose from the combined effects of many deletions among human ancestors. The study, published this week in Nature Genetics, goes on to find that these deletions contribute to lower blood cholesterol levels. The findings may also represent an interesting example of exon deletions that exert a beneficial effect on protein structure and human health.