In our guts.
Out of Africa and back (to some extent) and also again out of Africa into West Eurasia where it mixed with the Eurasian component. All of which is identifiable also in more specifically human markers like Y-DNA or mtDNA.
Yoshan Moodley et al., Age of the Association between Helicobacter pylori and Man. PLoS Pathogens 2012. Open access.
Ethio Helix has an extensive review of the entry so I'll be most succinct here.
There are more nice images in the paper but this one above probably expresses it all:
- Hp Africa 2 is found among Southern African natives (Khoisan)
- Hp Africa 1 is found among West Africans and Bantus (with some penetration in the Khoisan stomachs)
- Hp NE Africa is found at the Middle and Upper Nile and Lake Chad
- Hp Europe is found also in West Asia and North Africa and shows clear signs of being a hybrid of NE Africa and Asia2 (so it's phylogenetic position is a blend of its parents')
- Hp Asia2 is from South Asia
- Hp East Asia and Hp Sahul (Australasia) need no further explanation
My main contempt is the insistence on unrealistic molecular-clock-o-logic age estimates, which are clearly miscalibrated because the migration out of Africa took place some 90-80 thousand years ago at the latest and not 55 Ka ago as they suggest with basis. Otherwise the pattern of flows must be as they described... but add at least 50% to all age mis-estimates to make sense:
It is interesting that no exogenous lineage from Neanderthals nor Erectus/Denisovans have been identified. Did we have sex but shared no saliva? Hmmm...