Birds, like bats, have high metabolic rates due to the demands of flight but are also long-lived in comparison to similarly sized members of other species. This has a lot to do with mitochondria and membrane fatty acid composition, as shown by the evidence in the paper linked below. The membrane pacemaker theory of aging tells us that the genetically determined ratios of specific fatty acids in cell membranes determine resistance to oxidative damage, as well as other important properties in the operation of metabolism that are particularly relevant to mitochondrial function and the ways in which mitochondria become damaged in aging. From a practical point of view, this is one of the things that should steer our attention towards mitochondrial DNA damage as an important contribution to aging, and cause us to prioritize research on methods of repair of that damage.
The evolution of lifespan is a central question in evolutionary biology, begging the question why there is so large variation among taxa. Specifically, a central quest is to unravel proximate causes of ageing. Here we show that the degree of unsaturation of liver fatty acids predicts maximum lifespan in 107 bird species. In these birds, the degree of fatty acid unsaturation is positively related to maximum lifespan across species. This is due to a positive effect of monounsaturated fatty acid content, while polyunsaturated fatty acid content negatively correlates with maximum lifespan. Furthermore, fatty acid chain length unsuspectedly increases with maximum lifespan independently of degree of unsaturation. These findings tune theories on the proximate causes of ageing while providing evidence that the evolution of lifespan in birds occurs in association with fatty acid profiles. This finding suggests that studies of proximate and ultimate questions may facilitate our understanding of these central evolutionary questions.