An adaptive hypothesis for the evolution of the Y chromosome

H. Allen Orr, Yuseob Kim

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


Population geneticists remain unsure of the forces driving the evolution of Y chromosomes. Here we consider the possibility that the degeneration of the Y reflects its inability to evolve adaptively. Because the overwhelming majority of favorable mutations on a nonrecombining proto-Y suffer a zero probability of fixation, the fitness of the Y must lag far behind that of the recombining X. At some point, this disparity will grow so large that selection favors an increase in the expression of (fit) X-linked alleles and a decrease in the expression of (unfit) Y-linked alleles. Our calculations suggest that this process acts far more rapidly than hitchhiking-induced erosion of the Y and at least as rapidly as the fixation of deleterious alleles on the Y by background selection. Most important, this hypothesis can explain the evolution of Y chromosomes in taxa such as Drosophila that have very large population sizes.

Original languageEnglish
Pages (from-to)1693-1698
Number of pages6
Issue number4
StatePublished - Dec 1998


Dive into the research topics of 'An adaptive hypothesis for the evolution of the Y chromosome'. Together they form a unique fingerprint.

Cite this