The penis is an incredibly diverse and rapidly evolving structure, such that even in closely related species that otherwise differ very little in their morphology, penis form can be highly differentiated. Penises are also much more complex than their fundamental function — sperm transfer — would seem to require. The rapid divergent evolution of male structures is typically the signature of traits under sexual selection and the current evidence suggests the penis is no different in this regard. Despite the general agreement that sexual selection is the main driver of penis evolution, many questions about penis evolution remain unresolved. Furthermore, the penis might be an ideal characteristic on which to focus in the drive to link phenotype with genotype.

阴茎是一个极其多样且迅速发展的结构，因此，即使在紧密相关的物种中，如果它们在形态上差异不大，则可以高度区分阴茎的形式。阴茎也比其基本功能-精子转移-复杂得多。男性结构的快速发散演变通常是性选择下性状的特征，而目前的证据表明，在这方面，阴茎没有什么不同。尽管人们普遍同意性选择是阴茎进化的主要驱动力，但有关阴茎进化的许多问题仍未解决。此外，阴茎可能是理想的特征，可以集中在驱动器上以将表型与基因型联系起来。