From the middle of the twentieth century, the discovery of the structure of the main hereditary material - DNA, the sequencing technologies of DNA, and protein sequences has led to the unprecedented development of molecular biology and medicine. The development of appropriate programs and computers for the processing of a large amount of data obtained from the researches in these fields has led to revolutionary results not only in biology and medicine but also in other areas where the study of biological materials is important. One of these revolutionary discoveries was the discovery of the DNA isolation method from the ancient biological remains, called ancient DNA (aDNA), and reading of these DNA sequences, which led to the emergence and development of some fields of science as molecular anthropology, evolutionary genetics, paleogenetics, etc. A comparative study of the aDNAs sequences with modern DNA sequences has provided answers several interesting questions, especially about human ancestors, their historical evolution, and migration, and allowed us to propose new hypotheses with a reliable scientific basis. The purpose of this article is to provide a wide range of popular scientific information about ancient DNA, its isolation, problems, applications, use in various anthropological researches, and several features. The article also provides detailed information on the reading of the genomes of Denisovan and Neanderthal subspecies, one of the ancient ancestors of modern man, the migration of these species based on genome data, their role in the formation of modern humans, and their contribution to the modern human genome. In addition, the article discusses some of the genes and gene clusters inherited from Neanderthals and related to risk factors for COVID-19, as well as interesting literature data on the relative distributions of these genes and genome segments in different continents.