mmmscience writes "http://www.examiner.com/examiner/x-1242-Science-News-Examiner~y2009m7d28-Mammalian-genome-is-shrinking Unlike their leafy and hairless counterparts, mammals have contracting genomes. It is due to a lack of new transposable elements, those lovable jumping genes that viruses dump into the genomic code. While a human's DNA is still made up of 45% of transposable elements, they are mostly very old. Natural selection has seen mammals incorporate fewer new transposable elements than plants and nonmammals."
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