Phoenicians in West Africa at Phoenicia.org at http://phoenicia.org/phoewestafrica.html (covering The Periplus of Necho, The Periplus of Hanno, Carthage & Chami).I am in accord with the "out of Africa" hypothesis for initial human migration to other parts of the world -- see my posting at http://humanmigrations.blogspot.com/2009/03/human-migrations-and-principles-of.html but that was much earlier than seafaring or the megaliths, as the initial human migration "out of Africa" appears to have started ca. 60000 BC or so, if I understand DNA studies correctly.
From the Red to the Med, The Phoenicians in East Africa at Phoenicia.org at http://phoenicia.org/phoeEastAfrica.html
Ancient India, West Africa & the Sea at Migration Diffusion at http://www.migration-diffusion.info/article.php?year=2011&id=245
East Africa & the Sea in Antiquity at Stewartsynopsis.com at http://www.stewartsynopsis.com/east_africa.htm
West Africa & the Sea in Antiquity at Stewartsynopsis.com at http://www.stewartsynopsis.com/west_africa.htm
However, I am not in accord with attempts to link the much later origins of seafaring or megaliths (as opposed to traveling by dugout canoes) to Africans, because I think that is simply not supported by the evidence.
Nevertheless, it is well worth reading Harry Bourne's writings, because he has collected a lot of material about ancient seafarers that is of value to analysis of ancient seafaring and the spread of the megaliths.
Thinking "out of the box", it occurred to me in reading about the Periplus of Necho viz. the Periplus of Hanno that something is seriously wrong in terms of chronology because the travels are dated otherwise by extreme volcanic activity witnessed by the seafarers. More forthcoming in the next posting.