Some types of human mitochondrial DNA are objectively better than others, as demonstrated by comparative absence or prevalence in specific population groups. As we move towards technologies capable of replacing age-damaged mitochondrial DNA, consider that we could also be receiving an upgrade - there is no known biological obstacle to completely replacing a mammal's mitochondrial DNA. The new DNA should simply pick up where the old DNA left off and mitochondria will continue to function as intended: "Elite athletic endurance ability involves multiple genetic and environmental factors, with little known about the specific genotypes involved. As a first step to finding genetic markers of endurance performance, we recruited 66 male endurance runners and 110 control athletes. We investigated the distribution of m.5178CA polymorphisms [in mitochondrial DNA] in male endurance runners. Although the m.5178A genotype has been reportedly associated with longevity, endurance runners in this study showed a significantly higher frequency (71.2%) of the m.5178C genotype than control subjects (52.7%). The-m.5178C genotype may be favorable for performance in elite endurance runners."