Two potential migratory routes followed by modern humans to colonize Eurasia from Africa have been proposed. These are the two natural passageways that connect both continents: the northern route through the Sinai Peninsula and the southern route across the Bab al Mandab strait. Recent archaeological and genetic evidence have favored a unique southern coastal route. Under this scenario, the study of the population genetic structure of the Arabian Peninsula, the first step out of Africa, to search for primary genetic links between Africa and Eurasia, is crucial. The haploid and maternally inherited mitochondrial DNA (mtDNA) molecule has been the most used genetic marker to identify and to relate lineages with clear geographic origins, as the African Ls and the Eurasian M and N that have a common root with the Africans L3.
To assess the role of the Arabian Peninsula in the southern route, we genetically analyzed 553 Saudi Arabs using partial (546) and complete mtDNA (7) sequencing, and compared the lineages obtained with those present in Africa, the Near East, central, east and southeast Asia and Australasia. The results showed that the Arabian Peninsula has received substantial gene flow from Africa (20%), detected by the presence of L, M1 and U6 lineages; that an 18% of the Arabian Peninsula lineages have a clear eastern provenance, mainly represented by U lineages; but also by Indian M lineages and rare M links with Central Asia, Indonesia and even Australia. However, the bulk (62%) of the Arabian lineages has a Northern source.
Although there is evidence of Neolithic and more recent expansions in the Arabian Peninsula, mainly detected by (preHV)1 and J1b lineages, the lack of primitive autochthonous M and N sequences, suggests that this area has been more a receptor of human migrations, including historic ones, from Africa, India, Indonesia and even Australia, than a demographic expansion center along the proposed southern coastal
Odd that the authors refer to M1 as African, as they themselves point out it’s Eurasian in origin in another paper. However, they do radiate out of North Africa, so possibly that was what it meant.. see below.
I’m guessing that a lot of the M1’s you find across North Africa and the near East were brought up from upper Egypt with the expansion of the Halfan culture into the Levant and Maghreb, and got into Ethiopia via the Southern expansion of the same population, following the M78 Y chromosome. Although I expect quite a few in the near East were due to the slave trade on the East African coast too. This paper also describes M1b as North African, not Ethiopian (although they haven’t standardised the naming yet, so M1b is differently named in various papers).
Also interesting was the appearance of some ‘Australian’ Mt DNA.
However, the link found between the M Saudi 201 sequence and an M14 Australian sequence is puzzling. Although at first sight it could be taken as a signal of the connection between the two utmost ends of the southern route, it seems not to be the case. First, both lineages share three basal positions and this hypothetical link would considerably delay the arrival age of M in comparison to that of East Asia. It would be improbable that similar Australian links with other M lineages mainly from India were not found. Third, if the Arab lineage had such an old implantation in the Arabian Peninsula some detectable autochthonous radiation should be expected. Most probably, the M42 sequence belongs to an Australian clade and its related lineage found in Saudi Arabia is also of Australian origin. Historical links as those invoked to explain the presence of Indian and Indonesian sequences in the Arabian Peninsula pool should also be valid for this case. In our opinion, the camel trade between Saudi Arabia and Australia  could be a probable historic cause of this link. Future detection in Aboriginal Australians of other M42 lineages will confirm the Australian origin of this clade and its radiation age in that Continent. However, the link between the East Asia M10 clade  and the Australian M42 clade, if not due to convergence, seems to be more interesting as it would confirm, once more, the rapid expansion of macrohaplogroup M all along the Asian coasts [6,13]. The lack of autochthonous M and N lineages in the present day Arabian Peninsula populations confirms that this area was not a place of demographic expansion in the dispersal out of Africa .