Mutational changes in p53 correlate well with tumorigenesis.Remarkably,however, relatively little is known about the role that p53 variations may play in environmental adaptation.Here we report that codon asparagine-104 (104N) and glutamic acid-104 (104E),respectively, of the p53 gene in the wild zokor (Myospalax baileyi) and root vole (Microtus oeconomus) are adaptively variable,meeting the environmental stresses of the Tibetan plateau.