The book Guns Germs and Steel by Jared Diamond is loaded with myths and half truths on Africa. I am surprise no Africanist and Afrocentrist have been critical of this book. There are a lot of distortions in its broad general brush strokes.
Point 1: Sub-Saharan Africans were inferior to Europeans on first contact and could easily be conquered. This is false. Europeans could not conquer most African states until the latter part of the 1800s. From the 1400s to the 1880s, Europeans were mainly trading entities on the coast. Europeans were not able to conquer sub-Saharan Africa until the invention of the maxim gun. Plus, the places they inhabited were sparsely populated regions, not densely populated places like West Africa and Uganda for example.
Point 2: Because writing was not widespread, that put SSA Africans at a dis-advantage. First of all, writing is very African. Most Eurasian(Europe and Asia) scripts can be traced to Egyptian Hieroglyphs via the Proto-Siniatic script. Hieroglyph was also the script of the Sudanic Kushite Empire. The Meroitic Script is the second script to directly come from Hieroglyphs. No modern day script can be traced to cuneiform. Cuneiform died with the Assyrian Empire. Diamond gives more ink to cuneiform and Greek Linear A and B(insignificant scripts in the global scheme) than Hieroglyphs which most Eurasian scripts(Phoenician, Greek, Brahmi, Aramaic, Arabic) can be traced to directly or indirectly. He also seems to think that for a script to be usable or widespread, it must follow the Greek model of having vowels or "alphabetize." Numerous widely used scripts don't have vowels or are "alphabetize", like Arabic for example. Diamond claims that writing gave Europeans the advantage of communicating long distance. The implication is that SSA Africans could not communicate long distance without writing. This is very false. African languages are tonal in nature. With a pitch drum or talking drum, messages could be sent long distance. This unique African communication device was banned in the New World by slave owners.
Point 3: Europeans conquered sub-Saharan Africa about the same time they were conquering the Middle East, India, parts of China, and other Asian regions. Guns were widespread in SSA. Europeans were not the ones to introduce guns to SSA. Kanem-Bornu was the first SSA empire to acquire guns from its close ties to the Ottoman Empire.
Point 4: The Boers were not superior to all Africans and they did not conquer South Africa. They conquered the Khoisan, but were no match for the Bantu speaking states. Bantu speaking people were also armed with guns. In some cases, like the Xhosa, Boers were removed from Bantu land. They settled in regions that were depopulated by the mfecane/difaqane. It was the British Empire, after the 1880s, who conquered South Africa, with new military hardware, maxim gun. The Boers defeated the Zulus at Blood River, but dare not enter Zulu land. Dingane had cease using Shaka's military tactics. The Zulu's had defeated a far more superior force in the Battle of Isandlwana, the British.
Point 5: Diamond calls the innovations Eurasian(Europe and Asia), with North Africa being part of this, not surprising he claims all of North Africa as white, again a distortion. All of the innovations were centered in the Nile Valley(Africa), India, and Mesopotamia(Asia)for 2,500 years. European civilization only rose in the latter part of the 1st Millenium (330s BC) , with the rise of Alexander the Great.
Point 6: Gun Germs and Steel claims to be non-racial in its explaination of European domination. This is rather dubious. This is one of the most racialist works to come along in a while. Beginning a chapter on Africa with a title how Africa became black and making other racial claims is far from race biological neutrality. The Africa chapter in its Africa language map claims all the Horn of Africa and all Afro-Asiatic speakers as white. Diamond also claims Pygmies and Khoisans as a separate race from other blacks. Mr. Diamond Pygmies and Khoisans are not separate from other blacks just because of their height and in the case of the Khoisan skin tone, also. Dinkas and Neurs are exceptionally tall and dark, should they be separated from other blacks. Mediterranean Whites(Spanish,Italians, Greeks, Arabs, Turks, Persians, Syrians) are phenotypically distinct from northern and western European whites and have distinct haplogroups, should one view them as a separate race?
Point 7: Egypt dominated the Mediterranean for almost 2,500 years, and the Kushite Empire became a Mediterranean power, way before Cyrus the Great of Persia, Alexander the Great of Macedonia, and Rome. The centers of civilization were the Nile Valley(Africa), Indus Valley(Asia), and Mesopotamia(Asia), Africa and Asia. The Eurasian nomenclature is a distortion.
Point 8: Another myth is SSA was isolated from the rest of the world, pure rubbish. First of all the Sahara desert dessicated 5000 years ago, this is recent history with very little population effect. It was not a barrier before or after. All of Africa was connected via trade. Since ancient time Africa was always a source of raw material-- gold, ivory. Nubia/Kerma provide the ancient world with gold. Carthage became a wealthy Mediterranean power due to its trade links south of the Sahara all the way to the Senegal River. Axum which was among the four great civilization, on par with Rome, provided the world ivory and incense. Swahili, Mali, Ghana, Songhai, Kanem-Bornu, Great Zimbabwe provided the rest of the world with African raw material and slaves and also partook in the world's product. Eurasia has always been dependent on African raw material for its manufactured goods, as is today. Africa is not poor and does not lack "cargo", raw materials. Eurasia would not be able to produce her abundant "cargo" without African raw material, "cargo."
Point 9: There was no such thing as a unified "Bantu Civilization." There were several Bantu speaking civilizations: Kongo, Kuba, Luba, Lunda, Buganda, Rwanda, Burundi, Great Zimbabwe, Swahili, Zulu, Ndongo, Mutapa, Rozwi. All spoke a Bantu language. They were certainly not one civilization.
Point 10:European dominance, colonizaton of Africa lasted 70 years on average, not even a hundred years, but left significant changes. By the 1960s, most Africans had received independence. Conquest began around 1880s(about the same time conquest of Asia) and dominance lasted until 1960s, with the exception of Zimbabwe, Namibia, and South Africa.
Point 11: In my mind, the domesticated plants and animals had nothing to do with it. It had to do with technology-- maxim gun, quinine for treatment of malaria. The same technology that gave European an advantage in conquest of the Asian part of Eurasia. Most SSA societies were mature iron age societies, they could not be easily conquered like North and South America. Most SSA societies knew how to manufacture iron and some, even steel. Plus, the non-African domesticated plants that had massive impact on African populations(cassava and corn/maize) were not Eurasian. They were new world plants, introduced via trade with the Portuguese.
Point 12: Yes, SSA African used the Arabic script. The Arabic script spread due to trade and spread of Islam, same with the spread of the Latin and Cyrillic script, with the spread of Christianity in Northern and Western Europe, during the Medieval Period. Arabs never conquered SSA, or any Asian group. To a certain degree the spread of Christianity, caused the spread of the Latin script in SSA. But ultimately all these scripts can be traced indirectly to one African source, no matter how far away it is.
Conclusion: In my mind it was African germs(malaria), guns(widespread in SSA), and steel(the Haya made steel), that prevented European colonization of Africa for 400 years. If Bantu speakers weren't far away from the desert and there was no Sahara, I am sure Bantu shock troops would have conquered Eurasia. Hannibal did invade Eurasia with his elephants. His genius failed him. Instead of running back to defend Carthage, he should have sacked Rome creating and impasse. In this case it would be his genius that would brought about the conquest of Eurasia, not geography.