In almost every culture, women usually out live men. While several factors can influence the life expectancy differences between men and women, genetic makeup is considered to be the major reason women live longer than men. Mitochondrial DNA mutations cause males to age faster than females. Since mitochondrial DNA is only inherited from mothers, mutations that occur in female mitochondrial genes are monitored to filter out dangerous mutations. Male mitochondrial genes are not monitored so the mutations accumulate over time.