[An evolutionary hypothesis on the absence of the Diego antigen (Di-a) in Chibcha Amerindians]

Diego blood group was studied in 141 Amerindian and Eskimo tribes from Alaska and Canada. Twenty six tribes (18%) did not show the Di-a antigen and 20 tribes (77%) were of the Chibcha linguistic Phyla. In the past, the Di-a absence has been related to several ecological factors such as climate and the presence of clines. I advance an alternative explanation regarding the loss of the Di-a allele in the Chibcha genetic divergence which occurred 6000-7000 years ago, as a consequence of random processes and not of natural selection. It is postulated that the Di-a allele is absent in this Amerindian groups only, and that the presence of the antigen in four tribes (Boruca, Ica, Kuna and Sumo) is due to gene flow across neighboring groups of different languages which carry the Di-a antigen.