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Take a wild, common forest-dwelling mouse-like rodent, known as a vole, and subject it to 13 rounds of selection for increased aerobic exercise metabolism, and what do you get? A mighty “mouse ” with a 48 % higher peak rate of oxygen consumption and an increased basal metabolic rate, com-pared with unselected controls. Konczal et al. (2015) took advantage of an experimental evolution technique that has gained popularity, dubbed “evolve and resequence, ” to measure the genetic changes that pushed the humble vole to Olympian levels of perfor-mance. Overall, the changes within genes, as measured by differences in single nucleotide polymorphisms, were not dra-matic. Rather, the dominating adaptive response to this selection was in changed gene expression levels found in the heart (79 genes) and liver (278 genes) when compared with control voles. A set of candidate genes that mobilize sugars and fats from body reserves were identified (glycogen phosphorylase and debranching enzymes), along with those involved in stress responses and epigenetic changes. “Although some candidate genes points to enzymes with a changed structure, the results show that remarkable evolution of physiological performance can occur by regula-tory changes within basically the same biochemical machinery, rather than by changing the structure of enzymes, which are components of that machinery, ” said Konczal