Maternal variation in Huichol and Mixtec populations from Mexico

studying minor haplogroup D4h3a (Perego et al., 2009). Haplogroup D4h3a is spread only
along the Pacific coast of the continent, with a higher frequency in the South America. The
coalescence age of D4h3a is in agreement with the age when pan-American haplogroups
started their distribution all over both Americas. Thus D4h3a had rapidly with the others
founders migrated from Beringia along the Pacific coast (Perego et al., 2009). However, now
the genetic studies have revealed an existence of both simultaneous routes (Perego et al.,
2009; Haashiar Kashani et al., 2011).
The X2a and recently determined C4c haplogroups share a very similar phylogeography and
coalescence age estimates. X2a is restricted to northern North America, without any samples
found in south of USA. C4c is also distributed in North America, except two individuals from
Columbia. Both haplogroups have higher frequency in the Great Plains region. The estimated
age of C4c is 13,800 ± 3,800 ybp and the age of X2a is 18,600 ± 5,500 ybp, which is similar
when taking into account the standard errors. The contrasting distribution pattern of these two
rare haplogroups with D4h3a leads to a conclusion that there have been two migration paths -
X2a and C4c arrived to North America through an ice-free corridor between Laurentide and
Cordilleran ice sheets, while D4h3 was carried to southward along coastal migration (Perego
et al., 2009; Haashiar Kashani et al., 2011).
1.6 Middle America
Middle America, in a broad meaning, represents territories from the North to the South
America. It comprises the Southwestern USA, Mexico (including the Mesoamerica) and the
Central America, sometimes also Northeastern part of South America is included. The
Southwestern USA, Central America and Northeast of South America are geographic areas,
while the Mesoamerica is defined as a linguistic and cultural region, which extends from
middle southern Mexico to Costa Rica (because Mesoamerica is largely overlapping with
Central America, henceforth I will use term Mesoamerica also inferring to Central America)
(Figure 3). Although geographically close, northern and southern parts of Middle America
have had different roles in shaping population variation in this region.
Mesoamerica has been seen as geographical barrier between North and South Americas. It
played an important role during the colonization of the Americas, restricting the gene flow
between North and South America and thus shaping the diversity of founder haplogroups on
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