Winning by Losing in the Human Genome?
The idea that evolution is led by increasing genetic complexity has, over the years, annealed into the general opinion of geneticists. This increasing complexity is developed through the expensive and slow innovation cycle of gene duplication, mutation, and selection; and so, it seems contrary that a species’ fitness could be improved by losing hard-won genetic capabilities, as has been proposed by the “less is more” hypothesis (Olson, 1999). For that reason, genetic research has traditionally dealt with active genes instead of “broken” ones (or pseudogenes). The lack of a deep knowledge about the genomic significance of adaptive gene losses in mammalian genome evolution explains the important contribution of a recent study in this research area (Zhu et al, 2007). This recent work applied an ingenious method to systematically identify the losses of genes that had been long established in the human lineage over the last 75 million years. A total of 26 well-established genes, inactivated long after their birth, were identified by this analysis, with the identification of 16 previously uncharacterized human pseudogenes. This work completes former studies about pseudogene formation during human origin (Wang et al, 2006), and provides important insights for a better comprehension of this particular genetic phenomenon, in a field scarcely documented until now.
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