Abstract: Ancient DNA is DNA sequences extracted from ancient biological remains. This paper briefly reviews the 20-year history of ancient DNA study from its early period mainly with the technology of cloning to later use of PCR technology and the mature technology of extracting DNA from fossils. In the recent years, because of the emergence of many problems and fierce controversy in ancient DNA study, scientists began to consider the authenticity of ancient DNA and put forward some strict standards. Here, we discuss the significance and progress of ancient DNA studies involving anthropology, systematic and evolutionary biology, biological domestication, and archeology. The data from ancient DNA studies provide additional evidence to support former viewpoints such as the out of Africa theory . In the study of systematics and evolution, study of ancient DNA added valuable information about extinct biological groups and facilitated the reconstruction of phylogenetic relationships of organisms. Ancient DNA study also provided valuable insights into biological domestication and archeology of both domesticated animals and crop plants. Finally, perspectives and trends of ancient DNA study are reviewed.

Key words: Ancient DNA, Phylogeny, Evolution, Biological domestication