Long Trends—Rates of Innovation .................................................

LECTURE vi

One more example [of micro-innovations] may be the slow spread

of windmills. We ¿ rst get evidence of them in Persia late in the 1st

millennium C.E. And then they start to spread quite widely throughout

the Mediterranean, eventually in Europe.

B

y modern standards, change was slow in the era of Agrarian
civilizations. So it is all too easy to think of this as an era of stagnation.
Yet we have also seen that there was considerable long-term growth
in this period, and that suggests that there must have been a continuous trickle
of innovations. What factors encouraged innovation in the era of Agrarian
civilizations? Earlier lectures argued that collective learning—the ability
to share and accumulate learned information—is what makes our species
different. Ultimately, collective learning is the source of all innovation in
human history. Indeed, collective learning can generate cycles of positive
feedback, as innovations allow population growth, which increases the number
of people contributing to innovation. But speci¿ c features in each era and
region can also accelerate or slow the pace of innovation. This lecture discusses
four features of Agrarian civilizations that could stimulate innovation.

x Population growth.

x Expanding networks of exchange.

x Increasing market activity.

x The role of states.

Danish economist Ester Boserup (1910–1999) argued famously that
population growth can stimulate innovation, as those at the edges of
society are forced to seek new ways of feeding and supporting themselves.
During the 4,000 years of the later Agrarian era, human populations
multiplied by about ¿ ve times, growing from about 50 million to about
250 million people.