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From Africa to the Americas
Rene J. Herrera, Ralph Garcia-Bertrand, in Ancestral DNA, Human Origins, and Migrations, 2018
The Y Chromosome
Although Y chromosomes are usually examined using a number of genetic markers such as short tandem repeats (STRs), insertion/deletions (in/dels), and point mutations (one or a few nucleotide differences), they are ultimately characterized according to haplogroups or types. Scientists to characterize and compare extant and extinct human populations use these haplogroups as genetic markers. For example, the contemporary Y chromosome haplogroups of the general population of Pakistan are mainly R1a-Z93 (24.4%), J-P209 (15.3%), and L-M20 (13.1%). These three haplogroups represent over 50% of the Y types in Pakistan. In the Altaic populations, R1a-Z93 is the most abundant haplogroup, with frequencies ranging from 50.0% in the Southern Altaic to 11.8% in the Northern Altaic region. It is possible that these high R1a-Z93 frequencies represent the original migrations from the Near East via Pakistan to the Altaic. This is especially the case in relation to the Southern Altaic, considering the area’s reported genetic affinities to Southwest Asia.14 R1a-Z93 was transported by Bronze Age Indo-Europeans west of the Urals and into the plains and deserts of Central Asia and the metal-rich Altai mountain range. Thus, it is possible that R1a-Z93 signals an early Neolithic (approximately 12,000 ya) migration from the area of Pakistan into Central Asia and the Altaic. It is interesting that the R-M207, the ancestor haplogroup of R1a-Z93, is also thought to have originated in Southwest Asia, possibly before the LGM during the Late Paleolithic (26,800–34,300 ya).15 In a pertinent investigation, 24,000-year-old remains of a boy (the Mal’ta boy) belonging to haplogroup R-M207 were recovered from an area just east of the Altaic.16 This person was a member of a group of people that hunted big game in North Central Asia extending into Siberia during the Late Paleolithic at a time of extreme glaciation. These studies may suggest that people carrying haplogroup R-M207 were part of the original population of Southwest Asia and Pakistan that migrated to Central Asia. Overall, these results could be interpreted as evidence for two migrations, one early during the Late Paleolithic and a second one more recent, dating to after the LGM from Southwest Asia via Pakistan to North Central Asia and the Altaic.
Surprisingly, when the complete genome (entire DNA) of the 24,000-year-old Mal’ta remains and an additional individual from the Afontova Gora mountains dating to 17,000 ya17 were sequenced (genome-wide analysis), investigators found a surprisingly close affinity between Native Americans and modern-day western Eurasians that specifically link them to the Near East and no connection to contemporary East Asians.
Furthermore, it was estimated that approximately 14%–38% of current Native American ancestry derives from the West Eurasian populations represented by these two ancient individuals. These data support the contention that at least some of the Paleo-Natives that migrated to America initially originated from West Eurasia and not from Northeast Asia or extreme northeast Siberia. This information and the genetic connections to the Near East and Pakistan by way of the Altaic could offer an explanation for why several crania of Native Americans exhibit morphological characteristics that do not resemble those of East Asians but rather those of West Eurasia.18
Another pertinent Y chromosome marker, J-P209, originated in the Near East about 42,900 ya and from there it expanded into Pakistan and then North Central Asia.19 Although J-P209 is only present at 2.5% frequency in the Southern Altaic, this marker may represent genetic flow from the Near East as well. However, this marker does not appear in Native Americans, and thus, considering its low frequency in the Southern Altaic, it is possible that J-P209 dropped out via random chance (genetic drift) from the starting Asian Paleo-Native migrants before the Beringian crossing or it was lost from the founding populations after their arrival to America.
Pakistan and the Southern Altaic share a number of other Y chromosome markers as well. Of those, haplogroup Q-M242 and C-M130 are of particular interest as they are also found in America (Fig. 10.5).20,21 Q-M242 is the original mutation that gave raise to lineage Q, all other types of Q haplogroups derive from it. Q-M242 possibly originated in Central Asia approximately 31,400 ya, and from there it expanded to the north and west, eventually reaching the Altaic, northeast Siberia, and then the American continent. At the South West extreme of its range in Northern Pakistan, the frequency of Q-M242 ranges from 2.1% to 5.2%22 depending on the specific population in question. It is in Pakistan that the most ancient types of the Q haplogroup are seen, the less defined and older Q-M242 and Q-M346. The Q-M346 type derives from Q-M242 (the Q-M242 type is ancestor to Q-M346). Q-M346 originated in Central Asia. In the Northern Altaic, the frequencies of all haplogroup Q categories range from 68.0% to 40.7% and these individuals are almost totally of the Q-M346 type. Southern Altaic, on the other hand, possesses about 16.7% Q with all individuals belonging to the younger Q-L54 mutation.14 Considering the easterly progression in place of origin and the sequentially younger age of haplogroups Q-M242, Q-M346, and Q-L54, in that order, it is possible that these mutations occurred as humans migrated northeastward from the Near East toward Central Asia and the Altaics.
C-M130, the other Y haplogroup of importance, in relation to the Native American diaspora, may be Indian in origin and dates back to about 53,000 ya. It is postulated that carriers of C-M130 initiated a northward dispersal to Central Asia around 40,000 ya. It is found at frequencies as high as 8.2% in Pakistan.22 Its highest levels (75.5%) are observed in the Hazak of North Central Asia.21 All Pakistani individuals belong to the basal or most ancient type of haplogroup C (C-M130) or to the more recent mutation C2-M217. It is thought that the C2-M217 mutation originated about 12,000 ya in Central Asia23 and from that epicenter it spread in different directions. In the Southern Altaic, the frequency of C2-M217 is 20.0% while no haplogroup C has been detected in the Northern Altaic.2 All of the C haplogroups in the Southern Altaic is of the C2-M217 type. As with the Q haplogroup, it is likely that the younger C2-M217 mutation occurred in Central Asia or possibly in Southern Altaic from the ancestral, older C-M130. It is thought that Na-Dené-speaking peoples transported the C2-M217 mutation into the northwest Pacific coast of North America. Na-Dené-speaking groups are thought to have arrived in America from Asia 6000–8000 ya. Alternatively, others contest that this language family, that includes Athabaskan, Eyak, and Tlingit languages of Native Americans, developed earlier in Beringia, between the two continents, during a migrational hiatus.
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