AnthroNotes Volume 30 No. 2 Fall 2009
SIMULATING THE PAST TO EXPLORE THE FUTURE
byJ. DanielRogers
Throughout Earth's history there have been long
periods in which the climate was relatively stable
and other periods in which it was constantly
changing, sometimes rapidly. Climate, as part of the
environment, always has a deep impact on how people
live. For a very long time, but especially since the beginning
ofthe Industrial Revolution, people have played a significant
role in climate change. As we ponder our options for
developing a sustainable future, there is a profound need
to understand how people around the world may be able
to cope with change. But there is a problem; our
information from the past is fuzzy and incomplete. The
climatologists, for instance, who build projections for
understanding future changes, may have quality weather
data extending back only a few decades. Sometimes this
informaton is not enough when we seek to understand
trends occurring over the course of centuries.
At the National Museum ofNatural History some
of the scientists are turning to a new way to use the past to
see into the future. It is called Agent-Based Modeling, a kind
ofcomputer simulation that builds virtual societies in which
each individual person, or family, in the simulation behaves
according to social norms, but also in autonomous ways,
much as real people do. Working with social and computer
scientists from George Mason University, Smithsonian
anthropologists devised a model of the societies that herd
sheep, goats, camels, yaks, and horses on the steppe lands
of Central and Inner Asia. Like an elaborate computer
game, the agents (people) are born, get married, have
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AnthroNotes Volume 30 No. 2 Fall 2009
2000
50000 100000 150000 200000 250000 300000 350000Time in Days
children, visit their friends, share with family members whoare in trouble, remember their ancestors, and participate insocial groups. The agents also deal with problems, likedroughts, snow storms, and climate change.Using archaeological, historical, and ethnographicinformation on herding societies from around the world,each characteristic ofthe artificial society was painstakinglyprogrammed into the simulation using software calledMASON and Java. The first objective was to create an
artificial society inspired by the Bronze Age (2000 to 500B.C.) of Inner Asia. The people of the Bronze Age weremembers of clans and had leaders we might call chiefs,but not kings. Later, vast empires would emerge from theInner Asian heart land, culminating in the great MongolEmpire under Genghis Khan in the 13 th and 14th centuries.The Bronze Age ancestors of the Mongol Empire are thestarting point, a kind ofbaseline on which to build a historythat never happened, but could have.The second objective was to take the replica ofthe Bronze Age society and actually put time in motion
—
the clock starts ticking and does not stop for a thousandyears. On a very powerful computer this process takesabout 2 actual days. The graph on this page shows thepopulation changes for one ofthe simulated histories. One
thing to note right away is that a huge amount ofvariationand change is the norm. The human population is not evenremotely stable, nor does it decline or increase in a gradualway. Change is abrupt and sometimes catastrophic. Thething that accounts for most of this change is weather
—
snow storms and droughts. In Inner Asia these weatherevents sometimes kill nearly all ofa herder's animals. Whenthe animals die, the families cease to exist. This catastrophenearly happened around simulated year 330 ( 1 20,000 days)when the population dropped by 50% due to back-to-back winter snow storms and summer droughts.Even when climate is changing relatively quickly,
as today, what people must adapt to are the extremes.Herders today, just as in the Bronze Age, must find waysto buffer against catastrophes. They can do this bydeveloping a resilient economy. Although they cannot stopthe snow storms, they can migrate, share resources, anduse other strategies. One ofthe keys for the herders is havingflexible social networks that allow change, rather thanadhering to rigid behaviors—a good lesson for us all.Dan Rogers is Chair, DepartmentofAnthropology, NationalMuseum ofNatural History.
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