Researchers are comparing the biochemistry of long-lived species to better understand the roots of large differences in life span: "The team looked at the genome of more than 30 mammalian species to identify proteins that evolve in connection with the longevity of a species. They found that a protein, important in responding to DNA damage, evolves and mutates in a non-random way in species that are longer-lived, suggesting that it is changing for a specific purpose. They found a similar pattern in proteins associated with metabolism, cholesterol and pathways involved in the recycling of proteins. Findings show that if certain proteins are being selected by evolution to change in long-lived mammals like humans and elephants, then it is possible that these species have optimized pathways that repair molecular damage, compared to shorter-lived animals, such as mice. ... The genetic basis for longevity differences between species remains a major puzzle of biology. A mouse lives less than five years and yet humans can live to over 100 for example. If we can identify the proteins that allow some species to live longer than others we could use this knowledge to improve human health and slow the aging process."