Rodents evolve faster than humans in terms of nucleotide substitution rates, as shown by comparisons of 11 genes from rodents (mouse or rat) and humans with sequences from another mammalian species (usually bovine). The ratio of synonymous substitutions in the rodent lineage to that in the human lineage since their divergence is 2.0, while for nonsynonymous substitutions it is 1.3. Rodents also evolve faster in the 5' and 3' untranslated regions of five different mRNAs, with ratios of 2.6 and 3.1, respectively. The number of nucleotide substitutions between members of the β-globin gene family that were duplicated before the human-mouse split is also higher in mice than in humans, with the difference being greater for synonymous substitutions than for nonsynonymous substitutions. These findings support the neutralist view of molecular evolution over the selectionist view. The study uses a relative rate test to compare substitution rates in different lineages without requiring knowledge of divergence times. The results show that rodents have significantly higher synonymous substitution rates than humans, with the rodent lineage having about twice as high a synonymous rate since divergence. Nonsynonymous substitution rates are also higher in rodents, though the differences are less dramatic. The study suggests that rodents have shorter generation times and thus higher mutation rates, which may explain the higher substitution rates. However, the difference in synonymous rates is only 2-fold, which is less than the 100-fold difference in generation times, suggesting other factors may be at play. The study also examines the generation-time effect on different types of nucleotide substitutions. The effect is more pronounced on synonymous substitutions and nucleotide substitutions in noncoding regions than on nonsynonymous substitutions. The results indicate that the generation-time effect is weaker on nonsynonymous substitutions, which is consistent with the neutralist view of molecular evolution. The study raises concerns about the use of the molecular clock in estimating divergence times, as the generation-time difference between rodents and humans has only a 2-fold effect on the synonymous rate. This suggests that using an average mammalian rate may lead to over- or under-estimation of species divergence times. The study concludes that rodents have higher nucleotide substitution rates than humans, and this is likely due to factors such as shorter generation times and higher mutation rates. Other explanations, such as less accurate DNA replication systems, are also considered.Rodents evolve faster than humans in terms of nucleotide substitution rates, as shown by comparisons of 11 genes from rodents (mouse or rat) and humans with sequences from another mammalian species (usually bovine). The ratio of synonymous substitutions in the rodent lineage to that in the human lineage since their divergence is 2.0, while for nonsynonymous substitutions it is 1.3. Rodents also evolve faster in the 5' and 3' untranslated regions of five different mRNAs, with ratios of 2.6 and 3.1, respectively. The number of nucleotide substitutions between members of the β-globin gene family that were duplicated before the human-mouse split is also higher in mice than in humans, with the difference being greater for synonymous substitutions than for nonsynonymous substitutions. These findings support the neutralist view of molecular evolution over the selectionist view. The study uses a relative rate test to compare substitution rates in different lineages without requiring knowledge of divergence times. The results show that rodents have significantly higher synonymous substitution rates than humans, with the rodent lineage having about twice as high a synonymous rate since divergence. Nonsynonymous substitution rates are also higher in rodents, though the differences are less dramatic. The study suggests that rodents have shorter generation times and thus higher mutation rates, which may explain the higher substitution rates. However, the difference in synonymous rates is only 2-fold, which is less than the 100-fold difference in generation times, suggesting other factors may be at play. The study also examines the generation-time effect on different types of nucleotide substitutions. The effect is more pronounced on synonymous substitutions and nucleotide substitutions in noncoding regions than on nonsynonymous substitutions. The results indicate that the generation-time effect is weaker on nonsynonymous substitutions, which is consistent with the neutralist view of molecular evolution. The study raises concerns about the use of the molecular clock in estimating divergence times, as the generation-time difference between rodents and humans has only a 2-fold effect on the synonymous rate. This suggests that using an average mammalian rate may lead to over- or under-estimation of species divergence times. The study concludes that rodents have higher nucleotide substitution rates than humans, and this is likely due to factors such as shorter generation times and higher mutation rates. Other explanations, such as less accurate DNA replication systems, are also considered.