Original: Some of the key topics that spurred development of the field have been the evolution of enzyme function , the use of nucleic acid divergence as a '' molecular clock '' to study species divergence , and the origin of non-functional or junk DNA .
Simplified: Some of the key topics have been the evolution of enzyme function , the use of nucleic acid changes as a molecular clock to study species divergence , and the origin of non-functional or junk DNA .