24 Gut and Liver, Vol. 6, No. 1, January 2012 between Buddhist and Muslim groups.42 In India, a study using MLST of seven housekeeping genes found that most H. pylori isolates share significant homology with hpEurope strains, and the cag PAI revealed European ancestry as well.46 A recent study of H. pylori strains from Cambodia,47 analyzing the same seven housekeeping genes classified them in two groups, hpEurope and hspEAsia, and provided evidence supporting three ancient human migrations: 1) from India, introducing HpEurope into Southeast Asia, 2) from China, carrying hspEAsia, and 3) from Southern China into Thailand carrying hpAsia2. Their findings also support 2 recent migrations within the last 200 years: 1) from Chinese to Thailand and Malaysia spreading hspEAsia strains and 2) from Indians to Malaysia carrying hpAsia2 and hpEurope.47 A study of H. pylori isolates from Malaysia classi- fied them as hpEastAsia, hpAsia2 or hpEurope, and revealed a new subpopulation, hspIndia, within hpAsia2.48 In Oceania, there is evidence of two ancient migrations: one reached New Guinea and Australia, and a second, more recent, extended through Melanesia and from there to the Polynesian islands. These migrations were accompanied by two distinct H. pylori populations, hpSahul and hspMaori, respectively.41 After the European settling, the hpEurope predominates.49 THE AMERICAS PRE- AND POST- COLUMBUS It is thought that when humans traveled across the Bering Strait from Asia to North America, they were carrying H. pylori, and therefore, their descendants today should be carrying H. pylori strains with Asian genotypes. Consistent with this hy- pothesis, multiple studies including Native North American and South American H. pylori strains have found evidence of ge- netic similarity with Asian strains.43,50-53 The genetic diversity of the original settlers of the Americas has significantly increased mainly through the genetic flow of Europeans and Africans over the last 500 years. This is a fact extensively reflected in the H. pylori populations. 1. The colonization of the Americas The Spanish Crown sponsored three trips of Columbus, starting in 1492, to what they thought was a new route to the “Indias.” But instead of India they found the new American continent, at that time unknown to the Europeans or the Asians. The Spanish settlers brought not only political and social changes; they also transformed most Amerindian into mestizo populations (mixture of Amerindian and European ancestry). At present, the Amerindian component varies greatly, in propor- tion to the density of the original native population. In Mexico and Guatemala, where the density of the original population is greater, the Amerindian component is greater than in areas such as Southern Brazil and Central Colombia, with lower den- sity of original native populations.54,55 In general, mestizos in Latin America are mostly colonized by hpEurope strains and the original hpAmerind strains seem to be restricted to a minority of isolated Amerindian populations. As mentioned above, the H. pylori genome variants reflect the human demographic evolu- tion. 2. The slave trade H. pylori infection is ubiquitous in Africa, but gastric ulcers and gastric cancer are rare events.56 In the 16th century Por- tuguese merchants started exporting slaves from Africa to the Americas. African slaves had been brought to Europe for centu- ries, mostly from the Muslim dominated north coast. They were well educated and had a tendency to rebellion, which limited the trade. Slavery was also a traditional practice within some indigenous African societies.57 Various African kings operated several forms of slavery. When the foreign traders came with a demand for labor, West Africans swiftly developed an orga- nized trade.57 The exportation of African slaves to the Americas lasted about four centuries, reaching the largest numbers when the British, Spanish, French and Dutch traders joined the busi- ness. It is estimated that about 11 million slaves were forcefully recruited for the Atlantic trade. At least one million died during the voyage or soon after, mainly from malnutrition and diseases encountered during the forced marches and in slave camps. Most slaves came from West Africa and included multitude of ethnic groups representing north, central and southern West Africa.58 The identification of ancestry specific markers has al- lowed investigators to build reasonable hypotheses about the predominant H. pylori genotypes in the Americas before and after the Spanish expeditions to the New World.49,53 The original predominant H. pylori strains were apparently hspAmerind, a subpopulation derived from hpEastAsia. After Columbus and the following Atlantic slave trade, such strains are rare and there is a predominance of hpEurope in mestizos and hspWAfrica in African Americans and mulattoes (mixture of African and Euro- pean ancestry). In South America, H. pylori strains from Amerindians in the Venezuelan Amazon were compared to strains from a mestizo population from Caracas by examining three independent high- ly polymorphic H. pylori genetic loci. Amerindian strains were found to have genotypes related to East Asia, while the mestizo population harbored strains with Western patterns.52 Recent studies including H. pylori isolates from Mexican in- digenous groups show unique polymorphisms of the cagA and vacA genes revealing Asian, European and African sequences.50 Concatenated analysis of housekeeping genes showed that al- though many isolates clustered within the European groups, some strains clustered in a position intermediate between East Asian and European groups. They represent evidence support- ing that Amerindian strains are being displaced by European strains. This novel Amerindian group had been previously found in isolates from indigenous populations in Colombia (Huitotos), Venezuela (Piaroas), and Peru (Shimaa).50,51,59-61 However, mesti-