The second approach relies on isolating and analyzing DNA from an
ancient source, and comparing it to other ancient DNA or to modern DNA. In both cases, the number of differences between the DNA sequences of the two groups are determined, and these are used to draw conclusions about the relatedness of the two groups, or the time since they diverged from a common ancestor, or both.
The results of molecular anthropological studies are rarely used alone. Instead, the data are combined with information from fossils, archaeological excavations, linguistics, and other sources. Sometimes the data from these different sources conflict, however, and much of the controversy in anthropology centers around how much weight to give each when this occurs.
Advantages of Dna Comparisons
The essential postulate on which molecular anthropology is based is that closer genetic similarity indicates a more recent common ancestry. All organisms are believed to have evolved from a single ancestor. As different life forms evolved, their DNA began to diverge through the processes of mutation, natural selection, and genetic drift. Even within the same species, populations that do not interbreed will accumulate genetic differences, which increase over time. The number of these differences is proportional to the amount of time since the two groups diverged.
