20 - Migration of pre-Hispanic and contemporary human Mexican populations

Summary

There is considerable interest in determining the exact route(s) taken by populations that entered the Americas, which would be expected to be genetically linked to many Asian lineages. However, some of the lineages of these American ancestors that were likely lost by drift through time may be unearthed by mitochondrial DNA (mtDNA) sequencing of the ancient populations that are revealed in a growing body of fossils in America, including Mexico. The most recent common ancestors in America are identifiable because their lineages survived from one generation to the next and have started their differentiation by means of accumulated mutations, defining the founder mtDNA. Consequently, the genetic studies of human Mexican populations is a research area will inform us about genetic markers specific to each population, their movement, and their relationship through time (Davis et al., 2011; Ebenesersdóttir et al., 2011; Martins et al., 2011).

DNA is passed from one generation to the next; most of it is admixture, making each person unique from his or her parents. However, mtDNA passes from the mother to the child with no changes (with few exceptions). Mitochondrial DNA allows men and women to trace their maternal lineages; the non-recombinant region of the Y chromosome that passed intact only from father to son without any modification allows men to trace their paternal lineage. Both Y-chromosome DNA and mtDNA are subject to occasional mutations that become inheritable as genetic markers and then, after several generations, a particular genetic marker is carried by almost all male and female inhabitants of the region where it arose (Terreros et al., 2011; Wilder et al., 2004). When people leave this region, they carry the marker with them, allowing the tracing of migration patterns of a given person’s ancient ancestors. In addition, anthropological studies will complement genetic studies in answering the question of why people migrate. Because of the complexity of choosing every population in our study, we focus on the Mexican population, including the pre-Hispanic populations and the contemporary Mestizo populations. Accordingly, studying mitochondrial DNA will allow us to reveal the pattern of pre-Hispanic population migration. This is of particular importance since the American continent has been populated as a consequence of different migrations through time (Tarazona-Santos and Santos, 2002).