Genetic evidence generally includes mitochondrial, Y chromosomal and classical marker evidence derived from modern populations. One of the main issues to be considered when reviewing the data from genetic research is the relatively small data sets in addition to distinguishing patterns within the genetic DNA of modern populations when using them to determine ancient DNA patterns. Nevertheless the modern composition of the European gene pool appears to reflect these early colonising movements more strongly than any other demographic event in prehistory. It has been estimated that around 85 per cent of European mitochondrial sequences probably originated in the upper Palaeolithic of Europe. There have been a number of issues identified with early attempts to use DNA to track mobility of ancient peoples. These were primarily to do with contamination. However it must also be considered that this form of data is statistical and often is recorded and then displayed in huge quantities which in turn complicates the process. Y chromosome is the male line and the mitochondrial DNA is the female line. There is also the additional problem of time depth, as while it is possible to retrieve genetic patterns it is important to note that they are not defined or distinguished in terms of period of existence. So movement of people represented in the data reflects not just the Mesolithic-Neolithic transition but also movement of people in the time since then, such as during the Roman period (Zvelebil 2008). Data from protein markers (sometimes called 'classical' markers) are still more abundant than are data from DNA, although this situation is rapidly changing. Molecular genetic markers have provided previously unavailable resolution into questions of human evolution, migration and the historical relationship of separated human populations. Different evolutionary models are relevant to the different continents. Migration can profoundly affect genomic variation within a population. For most populations are rare exchange of marriage partners between groups occurs and an average of one immigrant per generation in a population is sufficient to avoid fixation of alleles. However, sometimes a whole population (or a part of it) may migrate and settle elsewhere. Thus the frequencies of alleles among the founders of the new population will differ from those of the original population and will inevitably differ again from those among which it settles. |
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