Life gave rise on our planet 3-4 billion years ago and since then, living organisms (from one cell to multicellular organisms) have undergone many genetic, phenotypic and communal changes. Scientists have been able to shed light on only a small part of this evolutionary process, but with the development of new techniques our knowledge is expanding day by day. For the past 30 years ancient DNA studies have aided us in understanding the molecular basis of the changes observed in living organisms. Ancient DNA (aDNA) is the genetic material obtained from biological remains (bones, teeth, plant seeds, etc.) acquired from archaeological and paleontological excavations. In the present review, molecular studies carried out to date, contributions of ancient DNA to medical sciences, as well as basic problems encountered in obtaining and using aDNA have been discussed.