I have not seen the megaliths in question so I must reserve judgment about them for the time being, but it is all very interesting in terms of megalithic origins.
Here is what I wrote about her important work on the Nigerian megaliths and their possible origin:
Africa, Ancient Megaliths and Seafaring Surveyors
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 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.
A megalithic origin in or near the heart of Africa, on the other hand, is unlikely because those peoples in the megalithic era lacked the seafaring technology necessary to transfer that technology across water to other countries. Evidence for ancient seaworthy boat-building is not found in regions such as Senegambia, Nigeria or the Central African Republic, where megaliths have been found. We do have such evidence in Africa, albeit in Egypt, as discussed below.
One group that is a candidate for being the ancient surveyor seafarers in question is mythical Jason and his Argonauts, who were so-called Minyans by origin -- more on this below.
In days before writing, people encompassed their history in oral accounts which later became myths and legends. Hence, it is possible that the legend of the Argonauts dates back to a true quite ancient event.
Legend also relates that the names of the Argonauts were subsequently inscribed in the stars of the heavens (e.g. Hercules), because the Argonauts used these stars for navigation, and, as I allege in Stars Stones and Scholars, also used those same stars to triangulate their land surveys of Earth (the full extent of such land survey(s) can be debated -- it may have been limited only to Europe and Africa originally).
The Book of Enoch relates as follows http://ftp.fortunaty.net/com/sacred-texts/bib/boe/boe064.htm:
"CHAPTER LXI of the Book of Enoch: Angels go off to measure Paradise:"Paradise" of course was the "heaven" of stars and Enoch gives us clear evidence that they were measuring land by cords (as in ancient Egypt) and "flew" , i.e. perhaps a bad translation for sailed by the wind and/or rowed on the waters.
1. And I saw in those days how long cords were given to those angels, and they took to themselves wings and flew, and they went towards the north.
2. And I asked the angel, saying unto him: 'Why have those (angels) taken these cords and gone off?' And he said unto me: 'They have gone to measure.'"
In Hebrew the word Minyan means "counter", "numberer" so that the Minyans conceivably took their name as the "counting" viz. "numbering" surveyors.
A current mainstream theory is that the Minyans originally came from Greece (Boeotia), but it is not really clear to this day where the Proto-Greeks originally came from, what their relation to e.g. the seafaring Phoenicians was, and one could even suggest that the argonautic Minyans may have came from pre-dynastic viz. early dynastic Pharaonic Egypt and/or the far North (Scandinavia), or even from the Ancient Near East.
I am thinking here particularly of the ships, the so-called "royal boats" (14 thus far) found buried at Abydos and dated to ca. 3000 BC (See http://www.abc.se/~pa/mar/abydos.htm). Such a great number of boats buried royally -- as if in honor of a common event -- might indicate that the Abydos royal boats were the boats that returned from the Minyan survey expedition. See here for more about Egypt and ancient shipbuilding: http://www.bible-history.com/links.php?cat=24&sub=364&cat_name=Ancient+Egypt&subcat_name=Naval.
Even assuming that the ancient seafaring land surveyors came from predynastic or early dynastic Pharaonic Egypt, i.e. Africa, the culture to which these seafarers originally belonged is thereby not necessarily clear. Ancient seafaring keeps being pushed further and further back by the archaeologists -- see http://www.archaeology.org/9703/etc/specialreport.html.
One argument against the ancient seafaring surveyors coming from early dynastic Pharaonic Egypt is that there does not appear to be the presence of writing carved in stone on these megaliths, which one would expect from a literate culture or civilization. When writing is found today, it is painted on the stone, and that is surely a later development on original, older megaliths. Hence, if the ancient seafaring surveyors came from Egypt, then it could only have been in an era where ancient writing was not yet discovered or perhaps was only in its scribal infancy.