Allan Dickerman, working under the supervision of Dr. John Kirsch at the University of Wisconsin-Madison, is using the technology of DNA-DNA hybridization to reconstruct the evolutionary history of rodents in the family Cricetidae and to test hypotheses concerned with the tempo and mode of evolution in this diverse and important family of mammals. The family comprises 369 species divided into 73 genera. Although the evolutionary history of the group is contentious, it appears to be divided into North American and South American Groups. This molecular level study will test hypotheses about the relationships of the North and South American lineages, relationships with Old World forms, relationships of tribes within the family, etc. The study will significantly increase our understanding of the origin of biodiversity within the New World, especially that of mammals.