My recollection is that Diamond's argument is slightly different. He argues that the east-west orientation of Eurasia meant that societies were more easily able to expand, because you experience relatively little climate variation moving along parallels than you do moving up and down meridians, which you are forced to do when you expand in a north-south oriented continent like America or Africa.

Similarly Eurasia had a wider variety of indigenous grains suitable for cultivation, and more large mammals suitable for domestication, and these could be taken with a population when the migrated (because of the aforementioned east-west orientation).

These advantages meant that populations were able to increase more rapidly, which necessitated an earlier development of agriculture, which lead to further productivity gains as improving food yields meant that people could spend more time developing more advanced technology.

The increased population densities had two further advantages - firstly, it meant that wars were more frequent, so Eurasians developed more advanced weaponry (the "guns" and "steel" of the title). Secondly, evolutionary pressures selected for resistance to diseases that could spread easily in crowded environments (the "germs").

So it's a little bit more subtle than just "our climate is inherently better for deep philosophical thoughts" or "our climate means that we are more productive workers".

It's usually called environmental determinism and is something no modern anthropologist or geographer really wants to be associated with (as much as a modern biologist would want to be associated with eugenics or phrenology).

GGS did cause some despair among academics, as century old discredited ideas were presented as science to the public.

http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4959.2008....

The popularity of the work Guns, germs and steel (GGS) has served to bring the question of human–environment connections once again to the forefront of popular thought. We assert that the recent success of GGS represents both a persistence of environmental determinist logic and a contemporary trend that privileges the environment as the primary influence on human–environment relationships. […] The book is found to mirror earlier environmental determinism by failing to take into account many of the advances in human–environmental thought since the early twentieth century. Its popular success suggests the pitfalls of failures to acknowledge the complex, intertwined and indivisible relationship that exists among humans and their environment. Furthermore, there is evidence that the environmental determinism espoused in GGS has caught the attention of international development policymakers potentially influencing future outlays of aid and assistance to the developing world. These conclusions raise cautionary flags against repeating past theoretical mistakes by accepting simplistic, causal explanations based largely on a deterministic conception of the natural environment.

> I'm too lazy to look for the actual references, but in one form or another climate-related arguments for the "superiority" of Europeans were made in the late 1700s and in the 1800s (and towards the end of the 1800s a more racist undertone emerged, but that's another story). Something like "one can only be productive in a temperate climate", while those poor souls that have to live at the Tropics will never become industrious peoples.

To be fair, the GGS arguments are about explaining the origins of different rates of development, and not giving a rationalization for continued supremacy. For instance, one of his major arguments was that the New World had few domesticated draught animals. That ceases to be of any relevance with modern transportation, or indeed modern industry. He is talking about why some countries got a headstart, not trying to establish some firmly rooted 'natural order'.