Or, as Yali put it so beguilingly in his famous question to Diamond nearly a third of a century ago: "why is it that you white people developed so much cargo and brought it to New Guinea, but we black people had little cargo of our own?"
To his credit, Diamond eschewed culture and looked to geography and ecology as the fundamental reasons for the disparity New Guineans and Europeans. Unfortunately, he got the wrong answers.
Much more on the other side ...
Although you'd never really know it from Diamond's book, or from the tv series, historians like William McNeill and Alfred Crosby have been asking pretty similar questions -- and coming up with pretty decent answers -- for more than forty years. While Diamond leans on their work in developing his thesis, he misses some critical points in the history of European development, and his argument is fatally flawed as a result.
Diamond's most serious flaw, in my opinion, is his inability to understand the early modern encounters between Africans and Europeans. Africans and Europeans have, in fact, been interacting for millenia. The Second Punic War, when Hannibal crossed the Pyrennees with elephants, demonstrates an active trans-Saharan trade all the way back in the third century BC.
The modern history of European-African interaction begins, however, with the Portuguese sea voyages in the thirteenth and fourteenth centuries. If Diamond were correct -- that Europeans had some deep-seated geopraphic advantage over Africans going back to the wheat-domesticated animal nexus, or to the layout of continents, or whatever -- you would expect those advantages to have manifested themselves at the time of these early contacts in the fourteenth century.
But they didn't. In their early contacts, the Africans owned the Europeans -- both figuratively, by defeating them in countless military engagements, and literally, by enslaving them when the Europeans violated the basic protocols of diplomatic interaction. It's worth noting that in the fourteenth century Europeans had firearms and Africans didn't. But the fourteenth-century firearms were basically useless militarily (crossbows were much more effective), and African advantages in numbers and strategy more than outweighed European guns.
Diamond has nothing on this stuff, but most historians who have written recently on the early years of European-African interaction -- such as John Thornton, Africa and the Africans in the Making of the Atlantic World or Herb Klein, The Atlantic Slave Trade -- discuss it extensively. One key result of European military ineffectiveness in this early period is the fact that Africans set the terms for the slave trade, a condition that existed at least until the nineteenth century. (Klein has a great discussion in his book on why so many more men than women were exported from Africa -- about 3:2. Historians used to believe it was because buyers in the Americas preferred men for their physical strength. It turns out that buyers perpetually requested women -- they wanted to breed slaves -- and European traders in Africa bought as many women as they could get, but the Africans wouldn't sell them women. The demand in African markets for women slaves was too great, and not enough made it to the coast for sale to Europeans. Some African traders also simply refused to sell women to Europeans as a general principle.)
Now, Diamond's argument about guns, germs, and steel is actually somewhat relevant for the conquest of America -- which happened about 150 years after the Portuguese began their maritime trade with Africa. I'm not as convinced by the guns and steel part, but most historians today are. I am totally convinced about the germs part -- Crosby proved it all the way back in 1972 when he wrote The Columbian Exchange: The Biological Consequences of 1492. He's got a great chapter on the devastating impact of smallpox on non-immunized populations -- a death rate of some 30% within three weeks of first exposure. But smallpox was only one element of a cocktail of diseases Europeans brought to the New World, and many others -- typhus, pneumonia, influenza -- had similar kinds of death rates in non-exposed groups. Africans, by the way, were generally immune to all these diseases, but Americans were completely wiped out. Spanish accounts of the conquest of the Aztecs, in fact, record that the empire's defenders were dying on the ramparts from smallpox, fighting the invaders with their last breath -- and forcing them to tear down the capital city brick by brick. It's been estimated that the population of Mexico declined from 20 million to 1 million within a century of the conquest, and the vast majority of that decline was due to epidemic diseases introduced by the Europeans.
The conquest of America spurred the commercial revolution in Europe, and the commercial revolution eventually spurred the industrial revolution. The industrial revolution, of course, had two phases: the early phase, in the eighteenth century, involved the mechanization of the production process and the introduction of the division of labor. The latter phase, in the nineteenth century, involved the application of steam power and the introduction of interchangeable parts.
Industrialization allowed Europe to achieve levels of productivity unheard of in world history, and it also spurred a degree of technological innovation the consequences of which we still live with today.
Europe's domination of Africa came after the industrial revolution. By the nineteenth century European firearms were lighter, easier to reload, and incredibly more accurate than the guns that had existed five hundred years earlier. Nineteenth-century guns gave Europeans a strategic advantage over Africans, an advantage they had lacked five hundred years previously.
In 1350 Europeans had no advantage over Africans, except for their knowledge of the Atlantic wind systems. By 1800 the European knowledge of wind had led, indirectly, to a commercial and industrial revolution, which in turn gave Europe the tools to defeat easily any and all opponents in the Eurasian-African immunological community.
The discovery of Atlantic winds, however, had very little to do with the foods Europeans ate, or the metals they used, or the diseases they had been exposed to. It had everything to do with the fortuitous location of the Canary Islands, the Azores Islands, and Portugal, and the fact that the Atlantic trade winds could take you from Portugal to the Canaries, that you could tack from the Canaries to the Azores, and that the North Atlantic Westerlies would take you directly back to Portugal. By learning this route (which took them the better part of 150 years), the Portuguese discovered how to navigate all the world's oceans, and set Europe on the path to world domination.
I'm not saying there's nothing of value in Diamond. If he had been a real historian, instead of just playing one on tv, he would have tied his argument into the existing historical literature and perhaps could have made a significant contribution to our understanding of the processes through which Europe came to dominate the world. As it is, though, real historians are going to have to go through his work carefully, sift out what's new from what's old, and separate out what's false from what isn't.
I will give him credit for popularizing some things that were already pretty well known, and getting people to think and talk about these important issues. I just wish he had done in a more intellectually honest way -- say like when Bill Moyers did his investigations into world religions.