Somebody mentioned Jared Diamond. I'll second that: the book is _Guns,
Germs, and Steel_, although _The Third Chimpanzee_ has some speculations
as well, some of which may have to be modified in light of a 400,000
year old wooden spear. On the other hand he figured Neaderthals weren't
related to us, and he might be proven right there.
Personally, I'd like to see Diamond and Jane Jacobs tackle this issue as
a team. WIth that off of my chest I'll try to outline the thesis.
Specifically we want to explain, preferably without referring to 'race',
why cities, writing, advanced metallurgy, agriculture, and charming
disearses, among other things, developed on the Eurasian continent, and
not on the other three/four (or to only limited degrees.) The dominant
factor he identifies is the size, orientation, and plant and animal
diversity of Eurasia. This allowed agriculture and thus oversized
cities, as well as heavy animal labor. Large concentrations of people
living with multiple species of animals exposed Eurasians to many more
diseases, which millenia later they were able to inflict on Americans
and Australians. Large cities could also boost technology. Widespread
trading networks were more feasible due to the size and geography of
Eurasia, including the east-west orientation allowing domesticated
plants to spread easily, Agricultural spread through Africa or the
Americas was harder, because more different climates were involved.
Why agriculture was mostly Eurasian in origin has to do with luck, or
possibly with greater diversity. Most of the world's large-seeded wild
grains lived in the Middle East. This kind of helped. Animals... well,
Diamond claims there are many traits a large species must have to be
domesticable, and most large mammals fail one of them. Most of the ones
which don't fail his traits are in Eurasia, and are the domesticated
species -- horses, pigs, cows, goats, and sheep, along with specialties
like yak and reindeer. The exception is the llama. He skips over dogs
for some reason -- perhaps not big enough. If you accept that it's
unlikely that any particular species will be suitable, it's easy to
explain why Australia and the Americas have no or one domesticated
species: most large mammals on those continents died off at about the
same time humans showed up. Given that these species had survived
several previous ice age cycles Diamond doesn't buy the climate change
explanation, and posits that when they met Cro-Magnon man without any
fear of large bipeds they turned -- briefly -- into walking
supermarkets.
Why Africa, with nearly as many species as Eurasia, should have none
domesticable, he doesn't touch. I'd suggest reversing the process --
having evolved with us for several million years, all the African
species are either too vicious (zebras) or too panicky (gazelles) to be
useful. As Eurasia only had hominids around for a million years (with
us not being terribly threatening hunters to anything which ran away) a
fraction of the species hadn't finished either evolving full defenses or
going extinct when we started accidentally domesticating them.
If the above wasn't entirely coherent, well, it's a dense book. I
recommend it. Well thought out, well argued, and with a good bit of
evidence. It might still be wrong, particularly in details -- there
might be overlooked evidence, or stuff might get superseded -- but it's
the most complex and plausible attempt as I know of. And he writes
well, I think.
Jacobs, in _The Economy of Cities_ plausibly reversed the usual
development process -- small trading cities developed first, near
unusual raw materials (obsidian, perhaps) and agriculture and animal
husbandry began by accident, due to the diversity and large number of
seeds and tamed animals brought in for trade. But this doesn't affect
Diamond much; we'd tack on that the trade cities of the Middle East were able
to develop farming early because the species in the area happened to be
most suitable. Then they spread through much of Eurasia because
climate, or at least day lengths, were similar. Allowing increased size
of cities and encouraging trade among cities, which in Jacobs' world is
what fosters their development in the first place, as they begin making
locally what they used to import. Throw in some diseases and you have
Eurasian civlization.
Merry part,
-xx- Damien R. Sullivan X-) <*> http://www.ugcs.caltech.edu/~phoenix
Beneath these hills great heroes lie
Of the Red Branch Knights and their ancient foe.
In still of night the immortals fight
But never the battle is won.