 Also, some highly variable segments are thought to be caused by balancing selection, but there are also studies against this hypothesis.Some of genome browsers and bioinformatic databases have a list of structural variations in human genome with an emphasis on CNVs, and can show them in the genome browsing page, for example, UCSC Genome Browser.Under the page viewing a part of the genome, there are "Common Cell CNVs" and "Structural Var" which can be enabled.