The Diego Blood group system was discovered by chance in 1953. At that time, a woman who lived in Caracas, Venezuela gave birth to her second child. The newborn became ill with hemolytic jaundice which was caused by an incompatibility between baby and mother's blood. The samples were sent fot analysis and the outcome wwas a new private antigen which was named after the baby, Diego (he died shortly after).
Further studies identified two different variants Dia and Dib. The first was found to be quite frequent among Amerindians and some Asian populations but absent among Caucasians, Africans and Australian Aboriginals. The second variant was common around the world.
Dia was also found among Polish people, and it is conjectured that it reached Europe via the Tartar - Mongol invasions in the 1300s.
The two variants arise from a mutation in the SLC4A1 gene. Where an amino acid change provokes Dia. As it is not found in all Asian populations it may have arisen in a confined area of Asia and moved into America with part of these people when they migrated into the New World.
In America there are two variants Di(a-) common in South America and NW North America while the other one D(a+) is found elsewhere. This may be due to the fact that the Di(a-) people are the remnants of a first wave of migrants, later over ran by a Di(a+) population. This theory was proposed by M. Layrisse and J. Wilbert  who wrote:
"The Diego blood group is an exclusive Mongoloid gene marker, although it is not present in all Mongoloid populations. The absence of the gene in Waica Indians and its very low frequencies in Warrau and Yaruro Indians of South America suggest that it represents a genetic characteristic of Marginal American Indians. Since Marginal Indians are considered to be early comers to the New World, we suggest that Diego-negative t populations were the first to arrive and to extend throughout South America, while the Diego-positive tribes came later."
Interestingly this theory would be completed by a later third wave that peopled the Arctic region where the Dia type is absent.
A recent paper by Bégat C, Bailly P, Chiaroni J and Mazieres S  gives another explanation:
"...For this purpose we assumed that the geographic distribution of the DI*A allele coding for Dia is not random but rather coincided with cultural traits according to the gene-culture comigration concept.
High frequencies were observed in the Peruvian Andes, on the Guyanese Plateau, in the southeastern Amazonian Basin, in a region comprising the Brazilian state of Pará, and along the Tapajos, Xingu and Araguaia tributaries of the Amazon River. Low frequencies occurred mainly in North America, in Chaco and at southern tip of South America. The DI*A allele was totally absent in the Arctic (Eskimo and Tlingit), Panama Isthmus (Bribri and Teribe), Tierra de Fuego (Alacalufe), and a few pocket areas in North America (Cherokee), Northern Brazil/Southern Venezuela (Ninam and Yanomama), and the Chaco area (Ayoreo, Zamucoan). 
They go on to explain that the Ayore suffered from a "severe founder effect", and this may explain the lack of DI*A in them. Then they explain its absence among the Panama Isthmus populatons because these Chibchan-speakers "predecessors have lived in isolation from Central and South Amerindians since the early Holocene" .
The Fuegians lack this allele because of "isolation by distance with ensuing drift"  and its void in Northern North America is due to a "Secondary migration ... of non-Amerind-speakers, i.e., Eskimo-Aleut and Na-Dene speakers, from Alaska to Greenland and Southwestern North America.", they back-migrated into Siberia too, and that explains the link between their language and the Yeniseian languages in Siberia where the Yeniseian speakers also lack the Di*A allele. Then came even more gene flow carrying the DI*B allelle into the boreal part of the New World.
- 5% Chinese
- 12% Japanese
- 54% South American Natives
- 4% North India
- 0.47% Polish
- 0.01% Other Caucasians
I must admit that the Diego blood Group is an oddity, found in many non-African It has an exclusively Amerindian variant the Dia variant but, and this is interesting: An antibody of the Diego antigen, Anti-Di(a), is the cause of hemolytic transfusion reactions and also of hemolytic disease of the newborn (like happened to the baby, Diego). The presence of this antigen, or Dia alloimmunization has been observed among different Asian and South American Amerindian populations. A study by Baleotti et al., (2014)  found that:
"...HLA-DRB1*07:01 allele was overrepresented in Dia-alloimmunized patients compared to nonimmunized patients and to healthy donors.
... Individuals carrying the HLA-DRB1*07:01 allele present an increased risk for Dia alloimmunization..."
This means that those with the lowest frequency of this type of HLA, which in the map below would mean those native to the areas shaded in blue or pale blue, would not have the Anti-Di(a) antigen, because they have Di(a). And the map is clear: The Americas and east Asia. But! why is Australia, Melanesia and Africa also blue?
Also the Altai region (i.e. Denisova-land) is blue. Could the Australia -Melanesia - Americas mean some Denisovan introgression? But what about Southern and Western Africa?.
Could this imply some introgression there, in Africa, of an archaic hominin? See my post an ancient Y chromosome lineage, which mentions a possible archaic-human admixture in a Nigerian site known as Iwo Eleru, where human skeletal remains with both archaic and modern features were found and dated to ~13 kya.
The map below shows the global distribution of DRB1*07:01:01:01, (Source).
And this is the image from  showing the distribution of the Diego factor in America (black = none, dark blue= high)
I have the impression that Diego factor is archaic, not the result of a bottleneck.
 M. Layrisse, J. Wilbert, Science (1961). Absence of the Diego Antigen, a Genetic Characteristic of Early Immigrants to South America, 13 October 1961, Vol. 134 no. 3485 pp. 1077-1078 DOI: 10.1126/science.134.3485.1077
 Bégat C, Bailly P, Chiaroni J, Mazieres S (2015) Revisiting the Diego Blood Group System in Amerindians: Evidence for Gene-Culture Comigration. PLoS ONE 10(7): e0132211. doi:10.1371/journal.pone.0132211
 Baleotti, W., Ruiz, M. O., Fabron, A., Castilho, L., Giuliatti, S. and Donadi, E. A. (2014), HLA-DRB1*07:01 allele is primarily associated with the Diego a alloimmunization in a Brazilian population. Transfusion, 54: 2468–2476. doi: 10.1111/trf.12652
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall ©