Reviewing the Evidence for the Unguarded X Hypothesis of Shorter Male Life Span

Why do males of all species have a shorter life expectancy than that of females? There are numerous perspectives on this question, from viewing it as a natural evolutionary outgrowth of mating strategies, to the more mechanistic concerns of differences in metabolism, appetite for risk, and so forth. One popular hypothesis is that the Y chromosome is less capable of covering for mutational damage to the X chromosome than is a duplicate X chromosome. This will gender-bias the effects of inherited mutations on the evolution of longevity, and perhaps also magnify the effects of stochastic mutational damage occurring across a lifetime. Experiments in using male mice engineered to have two X chromosomes provide supporting evidence for the proposition, and, as noted here, the balance of the rest of the evidence in the literature tends to follow along in that support. Researchers analysed all available academic literature on sex chromosomes and lifespan - and they tried to establish whether there was a pattern of one sex outliving the other that was repeated across the animal kingdom. Specifically, they wanted to test the 'unguarded X hypothesis' which suggests that the Y chromosome in heterogametic sexes - those with XY (male) sex chromosomes rather than XX (female) sex chromosomes - is less able to protect an individual from harmful genes expressed on the X chromosome. The hypothesis suggests that, as the Y chromosome is smaller than the X chromosome, and in some cases abs...
Source: Fight Aging! - Category: Research Authors: Tags: Daily News Source Type: blogs