Lecture 36: Comparing the World Zones
and many large mammals had been driven to extinction. Estimates of the
population of the Americas 500 years ago range widely from about 40
million to as high as about 100 million. In the Paci¿ c zone, migrants brought
agricultural technologies with them. However, on some of the smaller islands,
including Easter Island, agriculture eventually failed, leading to a return to
modi¿ ed forms of foraging. The total population of the zone is unlikely to
have exceeded 1–2 million.We have seen some striking differences in the historical trajectories of the
different world zones, including a very signi¿ cant demographic imbalance.
Five hundred years ago, populations ranged from about 400–500 million in
Afro-Eurasia to 50–100 million in the Americas, to just 1 or 2 million in
the Australasian and Paci¿ c zones. Nevertheless, there are also important
similarities. In each zone, human numbers increased as innovations allowed
humans to extract more resources from a given area. Even in Australia,
populations increased signi¿ cantly in recent millennia. So differences in the
histories of each region were at least in part a matter of timing rather than of
substance. Many of the differences reÀ ect differences in natural endowment,
in the size of local populations, and therefore in the “synergy of collective
learning” in each region. Differences in the pace and timing of change
would matter profoundly when the four zones were ¿ nally joined in the
last 500 years.We have seen that, despite important differences, there were also striking
parallels in the histories of the four world zones. The most important
was a universal long-term trend toward “intensi¿ cation”: innovation
characterized by the possibility of larger populations per given area and
increasing complexity. Ŷ